An apparatus for forming a three-dimensional image, the apparatus including a cartridge that stores ink which a printing head discharges and which has a photothermal conversion property; a conveying unit that conveys a thermally expandable material so as to pass the thermally expandable material through a first position where the printing head faces and so as to form an image on the thermally expandable material with the ink discharged by the printing head; and a light irradiating unit that emits light toward a second position which is in a downstream side from the first position in a conveying path of the conveying unit, so as to perform photothermal conversion. The cartridge is disposed at a position which deviates from an extending line of an irradiation path of the light irradiation unit.