A method for detecting light amount uniformity is applicable to a light-emitting device including a plurality of light-emitting elements. First, the light-emitting device is placed in a sensed region of a photo-sensing apparatus. Then, the following steps are executed N times: during the nth execution, turning on the (n+i×N)th light-emitting element, where i is 0 or a positive integer, n is less than or equal to N, and n and N are positive integers; detecting light emission of the light-emitting element with the photo-sensing apparatus to produce a scanned image; and finally, comparing whether the bright spots corresponding to the light-emitting elements in the scanned images produced through the N steps are consistent, and outputting an output signal indicating whether the light-emitting device is normal or abnormal.