An image pickup apparatus having a simpler hardware configuration and capable of operating by a smaller power consumption. The apparatus has an image pickup device for producing image data by photographing an image, a first storage device for storing image data obtained by the image pickup device, a size reduction circuit for reducing the size of the image data stored in the first storage device after reading out the image data, a second storage device for storing, in a unit corresponding to a predetermined number of lines, the size-reduced image data obtained by the size reduction circuit, and a single compression circuit for alternately performing, by predetermined timing, first compression processing and second compression processing to obtain two kinds of compressed data representing one photographed image, the first compression processing including reading out the image data stored in the first storage device and compressing the image data without reducing the size, the second compression processing including compressing the size-reduced image data stored in the second storage device.