A stereolithography apparatus that is configured to fabricate a three-dimensional model by forming a cured layer by irradiating an interface of a photocurable resin with light corresponding to sectional data of the three-dimensional model and stacking the cured layers includes a container holding the photocurable resin and having a constraining window configured to constrain the interface of the photocurable resin; a vertical movement table movable in a vertical direction orthogonal to the interface of the photocurable resin; an optical system configured to form the cured layer between the vertical movement table and the constraining window by irradiating the interface of the photocurable resin with light through the constraining window; and a position constraining mechanism configured to substantially flatten the constraining window by applying a force to the constraining window from the outside of the container when the cured layer is formed by the optical system.