A simulation device for a programmable controller is formed by realizing by software on a computer a virtual PLC for emulating operations of a real PLC, a tool that functions as a development aid device for the virtual PLC and an error simulator for emulating an error that occurs in the virtual PLC. The virtual PLC and the error simulator are structured such that the simulation device is adapted to set, without any operations by the tool, a specified condition at a corresponding address in an error memory of the virtual PLC by carrying out a specified error selection operation and a specified operation regarding presence and absence of error generation, based on a list display of error items on the computer screen, after causing desired PLC type data stored in a PLC type memory in the virtual PLC through the tool.