The present invention provides a PTO switch mode control device that is capable of performing appropriate idle shutdown when an engine is started, even in the case where an ignition switch is turned ON with a PTO switch ON when the engine is stopped. The PTO switch mode control device has: an ignition switch 3 that is turned ON or OFF to start and stop an engine 1; a PTO switch 4 that is turned ON or OFF to select switch a PTO mode that permits power takeoff, and an inactive mode that does not permit the power takeoff; and an ECU 2 that executes idle shutdown to stop the engine 1 when the engine 1 continuously idles for a predetermined time period, except for the PTO mode state. The ECU 2 functions to establish the inactive mode even when the PTO switch 4 is ON, when the ignition switch 3 is turned ON while the PTO switch 4 is ON, and subsequently establish the PTO mode when the PTO switch is switched from OFF to ON.