After calibration of the projector, the control circuit obtains a first position-data indicating the position of a feature point in the screen and a second position-data indicating the position of a feature point in a test image projected onto the screen. After acquisition of the first position-data and the second position-data, the control circuit obtains a third position-data indicating the position of a feature point in the screen and a fourth position-data indicating the position of a feature point in the test image projected onto the screen. Based on a difference between the first position-data and the third position-data, the control circuit corrects the position of a feature point in the test image contained in the fourth position-data to create a fifth position-data. Based on a difference between the second position-data and the fifth position-data, the control circuit recalibrates the projector.