An exposure control device is disclosed which has an extremely high accuracy as compared with the prior art, the error range being within a one-eighth step. For such a highly accurate control of exposure time, a value of exposure time to be determined is converted to a binary code of n bits, of which the lowest one bit is weighed one-eighth step. Based on the decimal number corresponding to the upper m bits of the binary code, the frequency of the control signal is adjusted and is used in reading out the lower (n-m) bits of the same binary code, whereby the period of actuation of the shutter is determined.