An electronic unit is provided. The electronic unit includes a circuit board provided with an electronic component and a terminal, a terminal holder fixed to the circuit board and holding the terminal, a first casing assembled so as to abut on the terminal holder, and a second casing assembled to the first casing so as to sandwich the terminal holder between the first casing and the second casing, and configured to maintain a state where the terminal holder and the first casing abut on each other by being engaged with the first casing so as to restrict movement of the first casing away from the terminal holder and by elastically pressing the terminal holder against the first casing through a pressing piece extending from the second casing.