A high-frequency integrating circuit 32 detects characteristics of horizontal high-frequency components and vertical high-frequency components of the image formed by a processing-target image signal. Based on the detection result, a CPU 61 obtains the number of bits of the after-compression-coding data of the image signal, and calculates the compression rate dependent upon the number of bits. The CPU 61 controls an image codec 36 so that the processing-target image signal is compression-coded through only one time of compression coding processing by use of the calculated compression rate. This configuration allows the image compression processing (compression coding) to be rapidly executed with high accuracy.