PURPOSE: To shorten the mold exchange time and consequently enhance the productivity by a method wherein a coincidence signal is issued in order to stop a rotary driving mechanism when the signal read at a reading section coincides with the signal set at a setter by a comparing both signals which each other.

CONSTITUTION: The No.3 cavity 53 is used for molding after the end of the molding by the No.1 cavity 51. When a start signal is issued so as to send through a data cavity No. setting section 33 to a cavity No. output section 34 in order to rotate a motor 15 and at the same time sent through an indexing position detecting section 37 to a comparator 38. When a marker 72 faces opposite to lamps or the like 74 with the rotation of a table 13, phototransistors or the like 75 send signals through the indexing position detecting section 37 to the comparator 38. When the signals sent from a setter 32 coincide with the signals sent from the phototransistors or the like 75 with the further rotation of the table, the comparator 38 sends a coincidence signal to the motor 15 in order to stop it.