A converter apparatus includes: a converter for converting an AC voltage into a DC voltage; a DC link capacitor connected to the converter; a voltage detector for DC link voltage; a charging circuit for the DC link capacitor; a charging circuit controller for a switch connected with a charging resistor; a current detector for detecting a current of the converter; a turn-on controller for controlling the turning-on of power devices; a switch for connecting or disconnecting a power supply; a power supply monitor for monitoring a connection state of the power supply; a threshold value setter for setting a first or second threshold value; and a failure detector for determining the presence or absence of the failure of the power devices by a comparison between a current flowing upon turning on the power device, immediately after disconnection of the power supply, and the first or second threshold value.