The inventive concept relates to a method for storing an image. The method includes: initially allocating an entire memory equally to a predetermined number of channels set to perform pre-recording for a first time period or a second time period shorter than the first time period when an event occurs; counting an event occurrence number from image signals input to the channels for a predetermined time period; and reallocating memory regions allocated to the respective channels, according to the event occurrence number and image signal storage states of the memory regions.