To provide an imaging device capable of preventing video recording from being started in photographer's unintended composition when the photographer is taking a still picture and switches to the video recording mode with a different aspect ratio.

When an instruction to start video recording is input with a video release switch 9c in taking a still picture, a system controller 15 performs control to make the aspect ratio of a conversion region set by a region setting unit 15i small gradually in the time series, fix the aspect ratio of the conversion region at the time when the aspect ratio of the whole image including a fixed region and the conversion region reaches a second ratio, and store the image data of photographed images generated after the time in a volatile memory 14 as video data.