A construction machine comprising: an electrical equipment (21, 22) installed in a vehicle body (2, 4); a urea SCR controller installed in the vehicle body (2, 4); and a battery configured to supply power to the electrical equipment (21, 22) and the urea SCR controller, wherein the construction machine further comprises: a plus-side main connection line configured to connect the electrical equipment (21, 22) and a plus terminal of the battery; a plus-side isolating switch provided on the plus-side main connection line configured to connect or disconnect the electrical equipment (21, 22) to or from the plus terminal of the battery; a key switch positioned at a downstream side of the plus-side isolating switch and is connected in series to the plus-side isolating switch, configured to connect or disconnect the electrical equipment (21, 22) to or from the plus terminal of the battery; a plus-side auxiliary connection line positioned at an upstream side of the plus-side isolating switch configured to connect the urea SCR controller and the plus terminal of the battery; a minus-side main connection line configured to connect a minus terminal of the battery to ground; and a minus-side isolating switch provided on the minus-side main connection line configured to connect or disconnect the minus terminal of the battery to or from ground. an electrical equipment (21, 22) installed in a vehicle body (2, 4); a urea SCR controller installed in the vehicle body (2, 4); and a battery configured to supply power to the electrical equipment (21, 22) and the urea SCR controller, wherein the construction machine further comprises: a plus-side main connection line configured to connect the electrical equipment (21, 22) and a plus terminal of the battery; a plus-side isolating switch provided on the plus-side main connection line configured to connect or disconnect the electrical equipment (21, 22) to or from the plus terminal of the battery; a key switch positioned at a downstream side of the plus-side isolating switch and is connected in series to the plus-side isolating switch, configured to connect or disconnect the electrical equipment (21, 22) to or from the plus terminal of the battery; a plus-side auxiliary connection line positioned at an upstream side of the plus-side isolating switch configured to connect the urea SCR controller and the plus terminal of the battery; a minus-side main connection line configured to connect a minus terminal of the battery to ground; and a minus-side isolating switch provided on the minus-side main connection line configured to connect or disconnect the minus terminal of the battery to or from ground. a plus-side main connection line configured to connect the electrical equipment (21, 22) and a plus terminal of the battery; a plus-side isolating switch provided on the plus-side main connection line configured to connect or disconnect the electrical equipment (21, 22) to or from the plus terminal of the battery; a key switch positioned at a downstream side of the plus-side isolating switch and is connected in series to the plus-side isolating switch, configured to connect or disconnect the electrical equipment (21, 22) to or from the plus terminal of the battery; a plus-side auxiliary connection line positioned at an upstream side of the plus-side isolating switch configured to connect the urea SCR controller and the plus terminal of the battery; a minus-side main connection line configured to connect a minus terminal of the battery to ground; and a minus-side isolating switch provided on the minus-side main connection line configured to connect or disconnect the minus terminal of the battery to or from ground.