A calibration method of a display executed by a display system including a display, an imaging device, and an information processing device, including an arithmetic circuit. In the calibration method, the arithmetic circuit: acquires a first captured image in a state in which no image is displayed by the display from the imaging device at the timing of initial calibration; acquires a second captured image in a state in which no image is displayed by the display from the imaging device at the timing of recalibration after the initial calibration; compares the first captured image with the second captured image; detects, as a result of the comparison, an area where a difference in luminance is a predetermined value or more, with an influence of an environment change; and when the environment change is detected, outputs a notification that the environment change has occurred.