a seat base (110) which is manufactured as a grid frame so that an electric vehicle battery (200) fixedly supported by a lower bracket (210) for assembling with a vehicle is loaded on an upper surface of the seat base (110) and shields front, rear, left, and right surfaces along an edge of the grid frame using a foldable shield sleeve (110a) attachable and detachable along the edge of the grid frame;

a plurality of support protruding parts (120) spaced a distance from each other and formed to protrude from a central portion of an upper surface of the grid frame of the seat base (110) to support a lower portion of the lower bracket (210) of the electric vehicle battery (200);

one or more anti-slip parts (130) which are installed in central portions of left and right end portions or central portions of front and rear end portions of the upper surface of the grid frame of the seat base (110), include foldable support plates (132), rotation of each of which is limited within a range of 90° from a horizontal position to an upright position based on a rotation shaft (131a) of a support (131), and prevent left-right slip and front-rear slip of the electric vehicle battery (200) loaded on the support protruding parts (120) of the seat base (110) when the support plates (132) stand upright and are pressed against a side portion of the electric vehicle battery (200) or a side portion of the lower bracket (210) of the electric vehicle battery (200);

ratchet accommodation recess parts (140) which are formed opposite to each other in two side surfaces of a front half portion or a rear half portion of the grid frame of the seat base (110), accommodate ratchets (150) therein, and expose battery fixing hooks (151) connected to leading ends of the ratchets (150) through hook through portions (141) connected to the upper surface of the seat base (110);

the ratchets (150) which are fixedly accommodated in the ratchet accommodation recess parts (140) and tighten belts (300) to fix the electric vehicle battery (200) to the seat base (110) in a state in which the battery fixing hooks (151) connected to the belts (300) are exposed to an outside through the hook through portions (141) of the ratchet accommodation recess parts (140) and inserted into assembly holes (211) formed in the lower bracket (210) of the electric vehicle battery (200) loaded on the upper surface of the seat base (110);

a corner support shaft (160) which is formed to protrude from a corner point of the grid frame of the seat base (110) to support and stack a lower portion of another seat base (110), of which left and right surfaces and a rear surface with reference to a front opening and an upper opening are closed, and in which a rotation shaft pin (161) is inserted into or separated from pin holes (161a) formed in the left and right surfaces; and

a post (170) which is inserted into and coupled to the corner support shaft (160) through the front opening or the upper opening of the corner support shaft (160) to be rotatable in a foldable manner, in which rotation of the post (170) is limited within a range of 90° from a horizontal position to an upright position based on the rotation shaft pin (161) of the corner support shaft (160), and which secures a loading space of the electric vehicle battery (200) between seat bases (110) to be stacked on each other when standing upright, and is separated from an inner portion of the corner support shaft (160).