An optical scanning apparatus comprising: a light source configured to emit light; a light deflector having piezoelectric drive portions, the light deflector configured to deflect the light emitted from the light source to perform optical scanning on a scannable region of a scan surface in a main scanning direction and a sub-scanning direction to form an image on the scan surface, wherein scanning in the sub-scanning direction is performed by driving a first group and a second group of the piezoelectric drive portions by a first drive voltage and a second drive voltage, respectively; a light receiver located in the scannable region and having a light-receiving surface configured to receive light incident on the scannable region over a predetermined range in the sub-scanning direction, wherein the predetermined range encompasses a plurality of scan lines such that, in a case of periodically uneven brightness of the image in the sub-scanning direction due to variation in the scanning speed of the light deflector in the sub-scanning direction, the number of scan lines in the predetermined range is greater, compared to a case of even brightness of the image in the sub-scanning direction; and a controller configured to calculate the number of times light is received by the light receiver within a predetermined period, the number of times light is received within the predetermined period being equal to the number of scan lines in the predetermined range, determine whether the calculated number of times of light reception is greater than a predetermined number of times, and, if it is determined that the calculated number of times of light reception is greater than the predetermined number of times, adjust a phase difference between the first drive voltage waveform and the second drive voltage waveform such that the number of times of light reception is restored to the predetermined number of times. a light source configured to emit light; a light deflector having piezoelectric drive portions, the light deflector configured to deflect the light emitted from the light source to perform optical scanning on a scannable region of a scan surface in a main scanning direction and a sub-scanning direction to form an image on the scan surface, wherein scanning in the sub-scanning direction is performed by driving a first group and a second group of the piezoelectric drive portions by a first drive voltage and a second drive voltage, respectively; a light receiver located in the scannable region and having a light-receiving surface configured to receive light incident on the scannable region over a predetermined range in the sub-scanning direction, wherein the predetermined range encompasses a plurality of scan lines such that, in a case of periodically uneven brightness of the image in the sub-scanning direction due to variation in the scanning speed of the light deflector in the sub-scanning direction, the number of scan lines in the predetermined range is greater, compared to a case of even brightness of the image in the sub-scanning direction; and a controller configured to calculate the number of times light is received by the light receiver within a predetermined period, the number of times light is received within the predetermined period being equal to the number of scan lines in the predetermined range, determine whether the calculated number of times of light reception is greater than a predetermined number of times, and, if it is determined that the calculated number of times of light reception is greater than the predetermined number of times, adjust a phase difference between the first drive voltage waveform and the second drive voltage waveform such that the number of times of light reception is restored to the predetermined number of times. calculate the number of times light is received by the light receiver within a predetermined period, the number of times light is received within the predetermined period being equal to the number of scan lines in the predetermined range, determine whether the calculated number of times of light reception is greater than a predetermined number of times, and, if it is determined that the calculated number of times of light reception is greater than the predetermined number of times, adjust a phase difference between the first drive voltage waveform and the second drive voltage waveform such that the number of times of light reception is restored to the predetermined number of times.