An oil level detection apparatus having a float-type oil level detector (50) and a mode switching unit. The oil level detector emits a signal indicating that the oil level has dropped when a movable contact disposed on a float (54) makes contact with fixed contacts once the level of oil (Lu) has dropped to a lower limit level. The mode switching unit switches between one of two modes selected from a first mode for actuating the alarm and stopping the engine (10) in accordance with the level drop signal, and a second mode for actuating the alarm and continuing to operate the engine (10) in accordance with the level drop signal.