PURPOSE: To provide a virtual controller which is portable, makes miniaturization possible and is capable of realizing largescale simulation as well without impairing versatility.

CONSTITUTION: This virtual controller 12 provides a mimic operation environment for an operation station 10 which makes a controller for executing the process control of a plant virtual and operates the plant via this controller. The virtual controller 12 includes a tool 19 for setting the simulation environment, an identifier for indicating the kinds of the simulation to be included in this tool 19 and to be executed and means 15 to 18 for judging the kind of the simulation to be executed from this identifier and preparing the simulation environment meeting this kind.