To provide a noise removal method for an image capable of effectively removing, by a few frames, luminance noise due to radiation and water droplet noise formed by reflection of fallen droplet, from an image captured under a high-dose and high-humidity environment.

According to the present invention, a representative configuration of a noise removal method for an image captured under a high-dose and high-humidity environment includes: continuously capturing images using an industrial endoscope that has an image pickup element at a distal end; removing luminescent spot noise by applying a median filter to images of respective frames; removing water droplet noise by applying a minimal value filter to the images of a plurality of frames to which the median filter has been applied; and removing white noise by performing an integration averaging process for a plurality of images to which the minimum value filter has been applied.