To provide a magnetic pattern detection device allowing enhancement of a gain without drastically increasing cost.

In this magnetic pattern detection device 100, when an amplification part 70 of a signal processing part 60 inputs a sensor output signal output from a magnetic sensor element 40 excited by an excitation signal and a reference voltage to an amplifier 71, a reference voltage generation part 72 generates a signal varying interlockingly with the excitation signal, and inputs the signal to the amplifier 71 as the reference voltage. The reference voltage generation part 72 includes a CR differentiation circuit 73 generating the reference voltage by differentiating the excitation signal. Because the reference voltage has a small difference with the sensor output signal output from the magnetic sensor element 40, the amplifier gain can be increased.