To provide an image forming device which is equipped with a bidirectional parallel interface, and aims at the expansion of printing functions.

A laser printer 1 handles from a negotiation phase of printing data which is transmitted under an ECP mode from hose devices HS1 to HSn to the next negotiation phase as one job by using a host I/F 21 which is the bidirectional parallel interface, and executes a following motion function which is registered in advance to the job. Therefore, the process can be performed by the job unit even to data to which a command such as PJL is not added, and at the same time, the following motion function which is registered in advance can be executed.