To carry out a favorable moving image exposure control while reducing electrical power required for holding the diaphragm position, in an imaging apparatus that drives a diaphragm by a stepping motor.

For the moving image exposure control, a decision unit determines presence of occurrence of the diaphragm driving (S204, S211). When a rotor and the magnetic poles of the stator do not face each other in a first operation mode, the control unit of the stepping motor drives a rotor to a facing position (S216), and shuts off the current in a coil (S215). When the diaphragm driving does not occur in the second operation mode, the control unit of the stepping motor shuts off the current in the coil at the state where the rotor of the motor and the magnetic poles of the stator face each other (S206). A holding current to be supplied to the motor is shut off in the first and second operation modes, thereby the lower power consumption can be achieved. In addition, the program profile of a diaphragm drive method and an exposure control is switched depending on the type of an imaging lens unit (S203, S210), thereby the favorable moving image exposure control can be achieved.