To provide an electronic device free of a risk that an electronic component is damaged by stress.

A circuit board 2 on which an IC chip 3 is mounted is put in a housing body 8. A top surface of the IC chip 3 is coated with heat conductive silicone gel 5. A heat sink 6 is inserted from an opening portion 8j formed on the housing body 8 and fitted to the top surface of the IC chip 3. Stress due to errors of a tilt and a mounting height of the IC chip 3 is never applied from the circuit board 2 and heat sink 6 to the IC chip 3, since the heat sink 6 can be fitted to the IC chip 3, after the circuit board 2 is stored in the housing body 8.