A crank angle detector in which a rotary body rotates in association with a crankshaft of an engine and has portions to be detected every predetermined angle and at least one of the portions to be detected is lacking, and first and second pickups positioned near the outer periphery of the rotary body with a fixed angle difference therebetween, for generating first and second pulses each time the portion to be detected passes. When a number of second pulses equal to or more than a predetermined number are detected after the first pulse has been detected, the crank angle detector sets the time the first pulse is newly detected, as a reference position time for a rotating angle of the crankshaft.