A fixing device (20) for fixing an image on a recording medium (P) includes an endless fixing rotary member (21) which is formed into a loop and comes into contact with the image on the recording medium, an opposed rotary member (22) which is in contact with the fixing rotary member, a nip forming member (24) provided inside the loop of the fixing rotary member to be in contact with the opposed rotary member via the fixing rotary member to form a nip portion to which the recording medium is fed in a feeding direction, a support member (25) which supports the nip forming member, and a heating source (23) which heats the fixing rotary member. The nip forming member includes a downstream portion extending downstream in the feeding direction from a center of the nip portion and an upstream portion extending upstream in the feeding direction from the center and longer than the downstream portion.