A fixation device includes: an endless belt member; a first roller arranged inside the belt member; a second roller arranged outside the belt member and biased toward the first roller via the belt member; and a pressure member is biased toward the second roller via the belt member. A facing surface of the pressure member that faces the second roller includes a first flat section and a second flat section that intersect at an intersecting portion. A first end portion of the first flat section on the opposite side to the intersecting portion, a second end portion of the second flat section on the opposite side to the intersecting portion, and the intersecting portion are on an imaginary arc in a cross-section. A radius R of the imaginary arc satisfies, with respect a radius Rp of the second roller, an inequality of “(1/2)×Rp≤R≤(19/20)×Rp”.