A ripple detection device 10 includes: a current detection part 11 that outputs a variation in an armature current as a voltage variation signal; a first smoothing circuit block 12 that extracts a current ripple component and a noise component from the voltage variation signal and outputs a first smoothing signal S1; a gain adjustment part 13 that adjusts the amplitude of the first smoothing signal S1 and outputs an adjustment signal VCA; a second smoothing circuit block 14 that corrects distortion of the adjustment signal VCA and outputs a second smoothing signal S2; a ripple detection part 15 that extracts only the current ripple component from the second smoothing signal S2 by removing the noise component therefrom and outputs a ripple component signal S0; and a digital signal conversion part 16 that converts the ripple component signal S0 into a digital signal.