A production method of a modeled object includes a fixing step of fixing a thermally expandable sheet onto a tray by entirely or partially fixing a periphery of the thermally expandable sheet placed on the tray by a fixing member; a thermally expanding step of thermally expanding partially the thermally expandable sheet, which is in a state of being fixed onto the tray by the fixing step, by being heated by irradiating the thermally expandable sheet with light by an irradiation unit, while moving the irradiation unit from a first position toward a second position unit; and cooling the thermally expandable sheet, which has been thermally expanded partially by the thermally expanding step, while maintaining the state in which the thermally expandable sheet is fixed onto the tray, while returning the irradiation unit from the second position to the first position.