An optical low-pass filter for a solid-state image sensor of an offset sampling structure is constituted of first and second optical members. The first optical member splits an incident light ray into a rectilinear ray and a refracted ray whose propagation direction is about 45° to a horizontal direction of the solid-state image sensor. The second optical member splits an incident ray into a rectilinear ray and a refracted ray whose propagation direction is about 90° to the horizontal direction. The optical low-pass filter having this configuration splits the incident light ray into four rays whose split points are at respective corners of a parallelogram. Assuming that Px represents a sampling interval in the horizontal direction, Py represents a sampling interval in the vertical direction, and D1 and D2 represent respective split widths of the incident light rays through the first and second optical members, the split widths D1 and D2 satisfy the following conditions: D1≈Px/{square root over (2)} and Py≦D2≦2·Py.