A user detecting apparatus includes: a memory; and a processor that executes a procedure, the procedure including: obtaining a first image and a second image, extracting a user-associated area from the first image according to a given condition, dividing the user-associated area into a plurality of areas, storing a histogram of each of the plurality of areas in the memory, detecting from the second image a corresponding area that corresponds to an area that is one of the plurality of areas and has a first reference histogram according to similarity, and changing a reference histogram used for a third image from the first reference histogram to a second reference histogram.