A developing device comprising: a developer bearing member rotatable while bearing developer on a surface thereof; a rotary body having a rotary shaft; a casing that contains the developer supplied to the surface of the developer bearing member to accommodate at least a portion of the rotary body; a rotary gear having an axial center parallel to the rotary shaft of the rotary body, the rotary gear being disposed outside a lateral wall of the casing to support an end of the rotary shaft of the rotary body; a stationary shaft member fixed to the lateral wall of the casing to rotatably support the rotary gear, an axial center of the stationary shaft member being collinear with an axial center of the rotary shaft of the rotary body; a rotary shaft supporter provided to an inboard end of the stationary shaft member to rotatably support the end of the rotary shaft of the rotary body, wherein the inboard end of the stationary shaft member is exposed to a space formed inboard of the lateral wall of the casing; a prevention member provided to the inboard end of the stationary shaft member to prevent the developer within the space formed inboard of the lateral wall of the casing from contacting the inboard end of the stationary shaft member, characterized in that the developing device, further comprises a bearing that rotatably supports the end of the rotary shaft of the rotary body, wherein the bearing is formed of a material having lower thermal conductivity than the stationary shaft member and is shaped to cover a part of the inboard end of the stationary shaft member exposed to the space formed inboard of the lateral wall of the casing. a developer bearing member rotatable while bearing developer on a surface thereof; a rotary body having a rotary shaft; a casing that contains the developer supplied to the surface of the developer bearing member to accommodate at least a portion of the rotary body; a rotary gear having an axial center parallel to the rotary shaft of the rotary body, the rotary gear being disposed outside a lateral wall of the casing to support an end of the rotary shaft of the rotary body; a stationary shaft member fixed to the lateral wall of the casing to rotatably support the rotary gear, an axial center of the stationary shaft member being collinear with an axial center of the rotary shaft of the rotary body; a rotary shaft supporter provided to an inboard end of the stationary shaft member to rotatably support the end of the rotary shaft of the rotary body, wherein the inboard end of the stationary shaft member is exposed to a space formed inboard of the lateral wall of the casing; a prevention member provided to the inboard end of the stationary shaft member to prevent the developer within the space formed inboard of the lateral wall of the casing from contacting the inboard end of the stationary shaft member, characterized in that the developing device, further comprises a bearing that rotatably supports the end of the rotary shaft of the rotary body, wherein the bearing is formed of a material having lower thermal conductivity than the stationary shaft member and is shaped to cover a part of the inboard end of the stationary shaft member exposed to the space formed inboard of the lateral wall of the casing.