A data line driver circuit includes a D/A converter circuit including a first gradation voltage selecting circuit controlling transistors of a first group to select a gradation voltage of a first polarity based on a first display data. A second gradation voltage selecting circuit controls transistors of a second group to select a gradation voltage of a second polarity based on second display data. A first gradation voltage signal line transfers the first polarity gradation voltage and a second gradation voltage signal line transfers the second polarity gradation voltage. A test switching circuit operates in response to a test signal to form a short-circuit between the first and second gradation voltage signal lines, to allow a leakage current to be measured between a drain and a source in each of at least one transistor of the first group and at least one transistor of the second group.