A power conditioner that is adapted to boost a direct current outputted from a first power supply, wherein the power conditioner converts the boosted direct current into an alternating current, and outputs the converted alternating current to a system power supply, the power conditioner comprising: a) a first boost circuit that comprises a first switch (Tra) configured to be connected between output terminals of the first power supply, and configured to boost the direct current from the first power supply by turning on and off the first switch; b) an inverter configured to convert the direct current outputted from the first boost circuit into the alternating current; c) a connection unit configured to connect an output side of the first boost circuit and an input side of the inverter; d) a controller configured to control voltage at the connection unit by turning on the first switch to set the output side of the first boost circuit to a voltage higher than a voltage on the input side of the first boost circuit, and thereby generating a short-circuit between the output terminals of the first power supply to form a first closed circuit of the first power supply; e) a short-circuit current value acquisition unit configured to acquire a first short-circuit current value passing through the first closed circuit during a period, when the controller turns on the first switch to set the output side of the first boost circuit to the voltage higher than the voltage on the input side of the first boost circuit; and f) a power supply abnormality determination unit configured to determine whether the first power supply has an abnormality based on comparison between the first short-circuit current value and a first reference current value, the first reference current value being previously fixed based on a characteristic of the first power supply. a) a first boost circuit that comprises a first switch (Tra) configured to be connected between output terminals of the first power supply, and configured to boost the direct current from the first power supply by turning on and off the first switch; b) an inverter configured to convert the direct current outputted from the first boost circuit into the alternating current; c) a connection unit configured to connect an output side of the first boost circuit and an input side of the inverter; d) a controller configured to control voltage at the connection unit by turning on the first switch to set the output side of the first boost circuit to a voltage higher than a voltage on the input side of the first boost circuit, and thereby generating a short-circuit between the output terminals of the first power supply to form a first closed circuit of the first power supply; e) a short-circuit current value acquisition unit configured to acquire a first short-circuit current value passing through the first closed circuit during a period, when the controller turns on the first switch to set the output side of the first boost circuit to the voltage higher than the voltage on the input side of the first boost circuit; and f) a power supply abnormality determination unit configured to determine whether the first power supply has an abnormality based on comparison between the first short-circuit current value and a first reference current value, the first reference current value being previously fixed based on a characteristic of the first power supply.