Fixing device

A fixing device comprising:

• a roller;
• a pressure unit configured to form a nip in combination with the roller, the pressure unit comprising:
• a belt configured to contact the roller in a nip region;
• a pressure pad configured to press the belt in combination with the roller;
• a side guide comprising an end guide surface, the end guide surface being configured to guide a side end of the belt;
• and
• a stay configured to support the pressure pad;
• an arm configured to press the pressure unit toward the roller;
• and
• a supporting member located on an outer side of the side guide that is opposite to an inner side on which the end guide surface faces, the supporting member being held between the stay and the arm, the supporting member comprising a contact surface which contacts the side guide and on which the side guide is swayably supported.