A captured image projection apparatus obtains projection parameters and image effect correction parameters from a moving image captured at a low resolution in a task different from a task in which capturing of a high-resolution still image is to be performed, when a change ceases to occur in the moving image and before the capturing of the high-resolution still image is started. The apparatus changes the scale of the obtained projection parameters from one for low-resolution image to one for high-resolution image. The apparatus applies an image conversion process and an image effect process to the captured high-resolution still image by using the projection parameters and image effect correction parameters obtained before the still image is captured. Thereby, the captured image projection apparatus shortens the time required from the capturing of the image to projection thereof.