A fixing device comprising: a fixing belt arranged rotatably around a rotation axis; a pressuring member arranged rotatably to come into pressure contact with the fixing belt so as to form a fixing nip; a pressing member facing to the pressuring member across the fixing belt; a guiding member coming into contact with an inner circumference face of the fixing belt and stretching the fixing belt together with the pressing member; a cap member attached to an end part (21a, 21b) in the axial direction of the fixing belt; an elastic member (29, 61) provided between the end part (21a, 21b) of the fixing belt and the cap member and positioned at an external diameter side of the end part (21a, 21b) of the fixing belt; and a detecting mechanism detecting rotation of the cap member, characterized in that the pressing member includes a pressing face pressing the fixing belt to a side of the pressuring member, the pressing face being inclined to the side of the pressuring member toward a downstream side in a conveying direction of a recording medium, the fixing belt includes a bulging part arranged at the downstream side from the fixing nip in the conveying direction of the recording medium, the cap member includes a facing part facing to the bulging part, in a situation before the pressuring member comes into pressure contact with the fixing belt, the bulging part is separated from the facing part so that a gap is arranged in an area arranged between the bulging part and the facing part, when the pressuring member comes into pressure contact with the fixing belt, the bulging part bulges toward an external diameter side of the fixing belt to fill up the gap because the pressing face is inclined to the side of the pressuring member toward the downstream side in the conveying direction of the recording medium, and the cap member is held by the end part (21a, 21b) of the fixing belt via the elastic member (29, 61) so that the cap member rotates with the rotation of the fixing belt. a fixing belt arranged rotatably around a rotation axis; a pressuring member arranged rotatably to come into pressure contact with the fixing belt so as to form a fixing nip; a pressing member facing to the pressuring member across the fixing belt; a guiding member coming into contact with an inner circumference face of the fixing belt and stretching the fixing belt together with the pressing member; a cap member attached to an end part (21a, 21b) in the axial direction of the fixing belt; an elastic member (29, 61) provided between the end part (21a, 21b) of the fixing belt and the cap member and positioned at an external diameter side of the end part (21a, 21b) of the fixing belt; and a detecting mechanism detecting rotation of the cap member, characterized in that the pressing member includes a pressing face pressing the fixing belt to a side of the pressuring member, the pressing face being inclined to the side of the pressuring member toward a downstream side in a conveying direction of a recording medium, the fixing belt includes a bulging part arranged at the downstream side from the fixing nip in the conveying direction of the recording medium, the cap member includes a facing part facing to the bulging part, in a situation before the pressuring member comes into pressure contact with the fixing belt, the bulging part is separated from the facing part so that a gap is arranged in an area arranged between the bulging part and the facing part, when the pressuring member comes into pressure contact with the fixing belt, the bulging part bulges toward an external diameter side of the fixing belt to fill up the gap because the pressing face is inclined to the side of the pressuring member toward the downstream side in the conveying direction of the recording medium, and the cap member is held by the end part (21a, 21b) of the fixing belt via the elastic member (29, 61) so that the cap member rotates with the rotation of the fixing belt.