Fade-in and fade-out device used in a cinecamera having an automatic exposure control circuit including a photoelectric element receiving light from scene through the diaphragm of the taking lens for generating an output voltage indicative of the scene brightness, a capacitor for generating an output voltage used as a reference voltage and a servoamplifier for comparing the output voltages of the photoelectric element and the capacitor so that an output, the sense of which is dependent on the values of the outputs of the photoelectric element and the capacitor and which is continuingly generated until both the outputs of the photoelectric element and the capacitor become equal to each other, is supplied to an actuating means for the diaphragm of the taking lens so as to control the same for the proper exposure. The fade-in and the fade-out device comprises a constant current charging circuit for selectively and additionally charging the capacitor with a constant current so as to increase the output voltage linearly to the source voltage thereby varying the diaphragm from the proper exposure aperture to the closed position so as to effect the fade-out, and a constant current discharging circuit for selectively discharging the capacitor with a constant current so as to decrease the output voltage linearly from the source voltage to the reference voltage thereby varying the diaphragm from the closed position to the proper exposure aperture so as to effect the fade-in. The constant current charging and discharging circuits permit the time period for the fade-in and the fade-out to be independent from the aperture of the diaphragm at the proper exposure while the exposure at the midpoint of the fade-in and the fade-out is made equal to each other.