A fixing device that includes a rotatable endless fixing member, a fixing heat source which heats the fixing member, a pressure member provided on the outside of the fixing member and facing the fixing member, a nip forming member provided inside the fixing member and forming a fixing nip between the fixing member and the pressure member, a nip forming support member for supporting the nip forming member, a high-thermal-conductive member provided between the fixing member and the nip forming member, an adhesive provided between the high-thermal-conductive member and the nip forming member. The thermal conductivity of the adhesive is larger than the thermal conductivity of the nip forming member and lower than the thermal conductivity of the high-thermal-conductive member.