The fixing device includes a rotary member for contacting the unfixed toner image, a pressure member for forming the nip portion by contacting the rotary member, and a cover for covering the rotary member with a space between the rotary member and the cover. In a cross section of the fixing device, the cross section being orthogonal to a generatrix direction of the rotary member, the shortest distance (H) between the nip portion and a farthest surface portion of the rotary member farthest away from a surface portion forming the nip portion of the rotary member, the maximum width (W) of the rotary member in the conveyance direction of the recording member, and an area (S) of the space in a range of the maximum width W in the cross section satisfy with a relationship of S/W≧0.7×H.