A detection apparatus (1, 101) configured to detect whether one of three switches (6, 6U, 6V, 6W) which allow a three-phase motor and an inverter to be disconnected from each other is in a short-circuit state, wherein each one of the three switches (6, 6U, 6V, 6W) is inserted into each of three bus bars in a serial manner, the three bus bars each connecting the three-phase motor and the inverter which drives the three-phase motor and which includes three sets of arm portions each including a high-side switching element and a low-side switching element being connected with each other in a serial manner between a first power supply line and a second power supply line that is connected at an electric potential lower than an electric potential of the first power supply line, the detection apparatus (1, 101) comprises: a switch determination resistor being provided between the first power supply line and at least one of three terminals included in the three-phase motor; a switch control portion configured to control the opening and closing of the switches; a detection portion configured to detect voltages of terminals which are included in the three switches (6, 6U, 6V, 6W), respectively, and which are connected to the inverter, and a determination portion; the detection apparatus (1, 101) being characterised in that said voltages of terminals correspond to voltages of the bus bars at respective points (X, Y, Z) between the inverter and the switches (6U, 6V, 6W); and the determination portion is configured to previously memorize the voltages of the terminals of the three switches (6, 6U, 6V, 6W) being acquired in a state where the three switches (6, 6U, 6V, 6W) are in an open state, and to determine a switch in the short-circuit state among said three switches (6, 6U, 6V, 6W) based on the voltages of the terminals of the three switches (6, 6U, 6V, 6W) as previously memorized by said determination portion and based on a detection result of the detection portion in a case where the three switches (6, 6U, 6V, 6W) are controlled by the switch control portion to be in the open state. a switch determination resistor being provided between the first power supply line and at least one of three terminals included in the three-phase motor; a switch control portion configured to control the opening and closing of the switches; a detection portion configured to detect voltages of terminals which are included in the three switches (6, 6U, 6V, 6W), respectively, and which are connected to the inverter, and a determination portion; the detection apparatus (1, 101) being characterised in that said voltages of terminals correspond to voltages of the bus bars at respective points (X, Y, Z) between the inverter and the switches (6U, 6V, 6W); and the determination portion is configured to previously memorize the voltages of the terminals of the three switches (6, 6U, 6V, 6W) being acquired in a state where the three switches (6, 6U, 6V, 6W) are in an open state, and to determine a switch in the short-circuit state among said three switches (6, 6U, 6V, 6W) based on the voltages of the terminals of the three switches (6, 6U, 6V, 6W) as previously memorized by said determination portion and based on a detection result of the detection portion in a case where the three switches (6, 6U, 6V, 6W) are controlled by the switch control portion to be in the open state.