PURPOSE: To make a memory low-capacity and simplify a control system, by a method wherein a point of time where a physical detected varied quantity has arrived at a sampling varied quantity or a sampling time whichever occurs earlier is made as a sampling point, and a value and time of its physical quantities each are detected at the same time.

CONSTITUTION: Sampling varied quantities dx1, dx2,..., dxn to physical quantities each are set up by a varied quantity setting instrument 2 and a fixed sampling time Ts is set up by a time setting instrument 3. On the one hand, the physical quantities each are detected at the same time during a molding cycle by sensors S1, S2,..., Sn and the detected physical quantities are monitored by a detection control part 4. Then the detection control part 4 detects values K1... of the physical quantities each and time t at the time is detected at a point of time when detected varied quantities dk1... of any of the physical quantities arrive at the sampling varied quantities dx1.... In addition, when the sampling time Ts is attained in advance, by the time when the detected varied quantities dk1... of the physical quantities each arrive at the sampling varied quantities dx1..., the values K1... of the physical quantities each and time t at this point of time are detected. Therefore, when the detections are repeated at the sampling points generated in order, the whole of sudden varied sections in physical quantities each are detected highly accurately.