To reduce the size and weight of an electronic circuit module that is constituted by housing a circuit board mounted with electronic components in an enclosure while the waterproofing property, moisture-proofing property, vibration damping property, and thermal diffusibility of the module is maintained without using any filler.

An enclosure base 2 and an enclosure cover 4, both of which constitute the enclosure, are respectively made of magnesium alloys having excellent vibration absorbability. At the same time, hydrophobic films 5 composed of, for example, an inorganic insulating material are formed on at least the power and/or electric signal inputting and outputting terminal sections of the circuit wiring formed on the circuit board 3 housed in the enclosure so as to cover the terminal sections. Consequently, vibrations given to the electronic circuit module from the outside can be reduced by the enclosure and water drops, vapor, etc., entering into the terminal sections from the outside can be cut off by the hydrophobic films 5.