A motor drive device in embodiments includes: a motor drive unit that generates a current for driving a motor on a basis of a position command and a position detection value of the motor; a motor-coil ambient-temperature estimation unit that calculates a motor-coil ambient-temperature estimation value by correcting an output value of a temperature sensor provided in a peripheral portion of a motor coil of the motor by using a filter including both a phase-lead characteristic and a low-pass characteristic; a motor-coil increased-temperature estimation unit that calculates a motor-coil increased-temperature estimation value on a basis of the current; and a motor-coil protection unit that limits the current on a basis of the motor-coil ambient-temperature estimation value and the motor-coil increased-temperature estimation value.