PURPOSE: To provide the positioning device of a molding die which realizes accurate positioning of a mold against a spraying robot and relaxes restrictions against automation.

CONSTITUTION: This is the positioning device of a forming mold in a FRP moldings manufacturing line on which a spraying robot is provided along a conveyor 12 loading the forming mold 13 and carrying it to a working stage. The positioning members 14 of the molding die 13 against the spraying robot are provided on the conveyor 12, mold positioning reference members 15 corresponding to these positioning members 14 are installed on measuring places separated from the conveyor 12, measuring instruments 16, 18 positioning the forming mold 13 against the mold positioning reference members 15 are provided on the measuring places, and an engaging member 22 engaging with the mold positioning reference members 15 in the condition in which the forming mold 13 is positioned against the mold positioning reference members 15 by means of the measuring instruments 16, 18 is adjustably provided on the bottom face side of the molding die 13.