Fixing device having a heating member and image forming apparatus including the same

In an image forming apparatus including a fixing device for fixing a toner image formed on a recording medium, said fixing device comprising:

• a rotatable member and a facing member forming a nip, which corresponds to a conveying zone, therebetween and configured to convey the recording medium via said nip for thereby fixing the toner image on said recording medium;
• and
• a heating member configured to heat said surface of said rotatable member in contact with said surface, said heating member including an endless belt in contact with the surface of said rotatable member,
• wherein a portion of said rotatable member and a portion of said heating member contacting each other respectively have a convex shape and a concave shape complementary to said convex shape.