A solar cell testing apparatus that tests bypass diodes in a solar cell string constructed by connecting a plurality of solar cell modules, which include solar cells and the bypass diodes, in series for failures in the open position, the solar cell testing apparatus comprising: a unidirectional element that is connected between a positive electrode and a negative electrode of the solar cell string with a polarity that permits passage of an output current outputted from the solar cell string when the solar cells generate power; a voltage applier capable of applying a test voltage, which has a voltage value that exceeds a sum of forward direction voltages of a plurality of bypass diodes and is a voltage such that a potential of the negative electrode is high relative to a potential of the positive electrode, across the positive electrode and the negative electrode of the solar cell string to which the unidirectional element is connected; a current detector that detects a current flowing in the solar cell string; and a processor executing: a process that measures a current value of a shorted current of the solar cell string based on the current detected by the current detector when the solar cells are generating power and there is a shorted state where the unidirectional element is connected between the positive electrode and the negative electrode of the solar cell string and stores a current value that is higher than the current value of the shorted current as a current threshold; and a process that tests for failures in the open position by comparing a maximum current value, which is measured based on the current detected by the current detector when the test voltage is being applied while the solar cells are generating power and there is the shorted state, and the current threshold. a unidirectional element that is connected between a positive electrode and a negative electrode of the solar cell string with a polarity that permits passage of an output current outputted from the solar cell string when the solar cells generate power; a voltage applier capable of applying a test voltage, which has a voltage value that exceeds a sum of forward direction voltages of a plurality of bypass diodes and is a voltage such that a potential of the negative electrode is high relative to a potential of the positive electrode, across the positive electrode and the negative electrode of the solar cell string to which the unidirectional element is connected; a current detector that detects a current flowing in the solar cell string; and a processor executing: a process that measures a current value of a shorted current of the solar cell string based on the current detected by the current detector when the solar cells are generating power and there is a shorted state where the unidirectional element is connected between the positive electrode and the negative electrode of the solar cell string and stores a current value that is higher than the current value of the shorted current as a current threshold; and a process that tests for failures in the open position by comparing a maximum current value, which is measured based on the current detected by the current detector when the test voltage is being applied while the solar cells are generating power and there is the shorted state, and the current threshold. a process that measures a current value of a shorted current of the solar cell string based on the current detected by the current detector when the solar cells are generating power and there is a shorted state where the unidirectional element is connected between the positive electrode and the negative electrode of the solar cell string and stores a current value that is higher than the current value of the shorted current as a current threshold; and a process that tests for failures in the open position by comparing a maximum current value, which is measured based on the current detected by the current detector when the test voltage is being applied while the solar cells are generating power and there is the shorted state, and the current threshold.