A distance measurement object is imaged by a pair of line sensors of an AF sensor, and sensor data showing the sensor images is generated. A CPU generates AF data showing the contrast of sensor images with the sensor data being sequentially acquired by the CPU for each cell. Then, the AF data is used to carry out calculation of correlation values or the like, thereby calculating the distance from the distance measurement object. Thus, generation of AF data for distance measurement calculation such as correlation value calculation showing the contrast of the sensor images formed by the pair of line sensors of the AF sensor, and distance measurement calculation using the AF data are carried out by the computation processing circuit (CPU) to simplify the circuit, and also the sensor data is sequentially acquired from the AF sensor, and at the same time the AF data is sequentially generated, whereby the amount of processing time for generation of the AF data is significantly reduced to shorten distance measurement time.