An engine unit having its early-start ability further improved with suppression of deterioration in mountability to vehicle. The engine unit includes a four-stroke engine body, a starter motor, a plurality of detection object parts, a rotor position detection device having a detection-purpose winding, and an inverter having a plurality of switching parts. A control device: shifts from a start control mode for performing on/off-operation of the plurality of switching parts at predefined timings to start forward rotation of the crankshaft, to an acceleration control mode for performing on/off-operation of the plurality of switching parts at timings based on an electrical signal flowing in the detection-purpose winding to accelerate forward rotation of the crankshaft; and in time periods during which the start control mode and the acceleration control mode are performed, causes rotation of the rotor to follow a variation in a current flowing in the multi-phase stator windings by controlling on/off-operation of the plurality of switching parts based on both a timing of a variation corresponding to the forward end of the detection object part and a timing of a variation corresponding to the rearward end of the detection object part among variations in the electrical signal flowing in the detection-purpose winding.