The invention relates to a device for measuring the thicknesses of liquid films. The device comprises an optical illuminating system, an image acquisition system and an image processing system. The optical illuminating system is used for irradiating on acquired objects; the image acquisition system is used for acquiring optical signals generated after the acquired objects are irradiated by the optical illuminating system and converting the optical signals into electric signals; the image processing system is used for comparing the electric signals of the acquired objects with electric signalsof calibration reference objects and obtaining the real thicknesses of the liquid films of the acquired objects by means of computing. The invention further relates to a method for measuring the thicknesses of the liquid films. The device and the method have the advantage that the detection time can be shortened by the aid of the device and the method.