An image resolution increasing method include setting a first block which is included in a low resolution image and is located at a first position, and a second block which is included in a high resolution image and is located at a second position, and setting, as an increasing resolution block of the first block, a third block expressed by a second vector obtained by projecting a first vector representing the second block to a linear manifold as a set of vectors that indicate fourth blocks of the second block size, the fourth blocks becoming the first block due to reduced resolution, in a Euclidean space having, as the number of dimensions, a product of the number of pixels arranged vertically in the second block size and the number of pixels arranged horizontally in the second block size.