A vehicular lamp system includes: an imager; a luminance analyzer that detects a luminance of each of multiple individual regions; an illuminance setting unit that determines an illuminance value of light emitted to each individual region, based on a detection result from the luminance analyzer; a light source unit; and a light source controller that controls the light source unit. The illuminance setting unit uses different functions to determine the illuminance value for an individual region that falls within a certain first luminance range, and the illuminance value for an individual region that falls within a certain second luminance range.