A magnetic sensor drive circuit that measures a magnetic field by passing a feedback current, which cancels changes in magnetic flux density using measured magnetic field, through a prescribed coil. The drive circuit includes: a first circuit block which controls the feedback current by using an external power source as a power source; a second circuit block which has an output adjustment circuit adjusting a signal according to the strength of the feedback current to be a signal proportional to the voltage of the power source; a first power source line which supplies the external power source to the first circuit block; a second power source line which supplies the external power source to the second circuit block in parallel to the first power source line; a first low pass filter; and a second low pass filter.