Fuser device and image forming device

A fuser device, comprising:

• a fusing member including an elastic layer on a surface side thereof and a cylindrical curved surface portion having a predetermined diameter;
• a heating member including a cylindrical curved surface portion having a predetermined diameter, the heating member having contact with the fusing member and heating the fusing member;
• and
• a pressure member including an elastic layer on a surface side thereof and a cylindrical curved surface portion having a predetermined diameter, the pressure member pressing the fusing member, wherein
• the fusing member and the pressure member sandwich a recording medium having an unfused toner image so as to fuse the unfused toner image,
• a surface temperature of the heating member is set higher than a setting temperature of the fusing member without disposing a heat generation source inside the fusing member,
• the diameter of the cylindrical curved surface portion of the fusing member is smaller than a diameter of the cylindrical curved surface portion of the heating member, and
• the diameter of the cylindrical curved surface portion of the pressure member is the diameter of the cylindrical curved surface portion of the fusing member or more.