An electronic component unit includes: a circuit board to mount an electronic component on the circuit board; a connector to receive and retain a terminal to be electrically connected to the circuit board; and a cover assembled to the connector and housing the circuit board. The circuit board is retained with the cover by using a beard retaining portion integrated with or separate from the cover. The connector has a cover retaining portion including a pair of protrusion portions. The cover retaining portion retains the cover assembled to the connector by holding a part of the cover between the pair of the protrusion portions.