A solid-state imaging device with an improved heat release-ability for releasing a heat generated in the amplifier unit of the solid-state image sensing element includes an elongated substrate (molded case 18), a metallic layer 16 exposed in a surface of the molded case 18 and extending along an elongating direction of the molded case 18, and an elongated solid-state image sensing element 20 mounted on the metallic layer 16, in which a thickness in a region of a metallic layer 16 right under an amplifier unit of the solid-state image sensing element 20 is larger than thicknesses in other regions of the metallic layer 16.