An image pickup apparatus including an image pickup device configured to convert a monitored object image into an electrical image signal and to output the image signal, a clock generator configured to generate a constant cyclic drive frequency to drive the image pickup device, and an external device configured to output a brightness signal based on a brightness of the monitored object. Further, a sensitivity to light of the external device is higher than that of the image pickup device. Also included is an image signal reading unit configured to synchronize the image signal with a frequency based on the drive frequency and to read the image signal in a constant read frequency, a brightness signal obtaining unit configured to obtain the brightness signal of the object from the external device, and a read frequency changing unit configured to change the read frequency based on corresponding to the obtained brightness signal.