(a) placing a first substrate or an edge ring on a fork of the transfer mechanism, transferring the first substrate or the edge ring to a target position, and placing the first substrate or the edge ring onto the target position;

(b) placing a second substrate having a position detection sensor on the fork, and transferring the second substrate to a position directly above or below the target position;

(c) detecting an amount of deviation between the first substrate or the edge ring and the target position, by using the position detection sensor of the second substrate; and

(d) correcting transfer position data of the transfer mechanism for the first substrate or the edge ring to be transferred next, based on the detected amount of deviation.