The range finder measures the distance to the object based on the principle of triangulation, and includes a pair of lenses; a lens supporting frame; a CCD supporting plate; CCD packages supported by the plate; and temperature sensors. One sensor is positioned on the frame between the lenses, and the other is positioned on the plate between the CCD packages. Each CCD package includes a CCD chip located at a focal plane of the lens, a casing and a transparent plate. The lenses, frame, casing and transparent plates are made of the same plastic material so that the thermal expansion of the entire range finder caused by the temperature change may not affect to the distance measurement. Bonding ribs connected to the transparent plate are located near an image ray hole to face each other and on the line perpendicular to the optical axis of the CCD chip and the plane containing the optical axes of the CCD chips. Therefore, the thermal deformation of the transparent plate in the base line direction of the range finder may not affect significantly. The range finder of the invention can reduce the distance measurement error caused by nonuniform thermal deformations of the parts.