PURPOSE: To provide an electronic circuit module wherein a case can be well mounted on a circuit board.

CONSTITUTION: An electronic circuit module 1 is composed of a circuit board 2 having a board 20 on which specified electronic circuit is formed and signal input/output part 21 of this circuit on one end face 20a and a case 3 mounted on the board 2 such that it surrounds two side end faces 20b and other end face 20c of the board 20. At one end face 20a of the board 20, at least, protrusions 22 are formed at a high working precision than that of the side end face 20b and positioning parts 31 are formed which contact with the protrusions 22 when the case 3 is mounted on the board 2 whereby the case 3 is positioned to the board 2.