To provide an image processor which can reduce noise while a frequency distribution characteristic of noise included in an image is maintained.

An image processor (10) includes: a first calculation section (11) for calculating similarity between a first region including a target pixel and a second region including a reference pixel and calculating a multiplication coefficient whose value becomes larger as the similarity becomes higher; a second calculation section (12) for calculating a random number (f); a product sum calculation section (13) for multiplying a pixel value of the reference pixel by the multiplication coefficient and the random number (f) and calculating a total sum of a multiplication result; a coefficient total sum section (14) for multiplying the multiplication coefficient by the random number and calculating the total sum of the multiplication result; and a division section (15) for dividing a calculation result of the product sum calculation section (13) by the calculation result of the coefficient total sum section (14).