An angular velocity measuring device measures an angular velocity of a gear that is fixed to a rotary shaft. The angular velocity measuring device includes a pair of magnetic sensors that are arranged at positions facing a tooth flank of the gear and that detect a shape of the tooth flank in a noncontact manner, and a computation unit that is configured to generate a waveform obtained by synthesizing output detection signals of the pair of the magnetic sensors with each other and output an output waveform and calculate the angular velocity of the gear from the output waveform. The magnetic sensors are arranged such that the output detection signals are offset from each other by {(n−1)+(⅙)} pitches when one pitch is defined as one cycle of the shape of the tooth flank in a circumferential direction of the gear.
