A method for forming an image sensor includes: providing a first device including a visible light receiving portion and an infrared receiving portion; coating a first infrared cutoff filter on the first device; patterning plural photoresists on the first infrared cutoff filter located in the visible light receiving portion to form a second device; etching the second device until a first filter of the first device is exposed to form an infrared cutoff filter and an infrared cutoff filter grid located in the visible light receiving portion, in which the infrared cutoff filter grid is located on the infrared cutoff filter; filling a color filter in the infrared cutoff filter grid and forming a second filter on the first filter; and disposing a spacer layer and a micro-lens layer on the color filter and the second filter sequentially.