PURPOSE: To provide the plant simulator which can easily simulate the operation of a plant to handle a solid by defining a material as one independent object and clearly expressing it as a material model.

CONSTITUTION: A simulator 16 to read the operational specification of a plant equipment from a data base 19 and to simulate the operation of the plant equipment with animations is provided with a material model 10 storing knowledge information concerning the material to be processed by the plant, and material operation inference part 4 to infer the operation of the material from the operational specification and corresponding to the animation, the operation of a controlled system is executed together with the operation of the solid-state material.