Disclosed is a method for crystallizing a silicon thin film, wherein the sizes of the crystal grains of the silicon thin film are made uniform. The method includes: a second step wherein a first gate electrode (2) having a first reflectivity is laminated on a substrate (1); a third step wherein a second gate electrode (3), which has a second reflectivity smaller than the first reflectivity, and which has an upper area smaller than that of the first gate electrode (2), is laminated on the first gate electrode (2) by having the upper surface periphery of the first gate electrode (2) exposed; a fourth step wherein a gate insulating film (4) is laminated by covering the peripheral region on a substrate (1) having no first gate electrode (2) formed thereon, a first region on the first gate electrode (2) exposed from the second gate electrode (3), and a second region on the upper surface of the second gate electrode (3); a fifth step wherein an amorphous silicon thin film (5a) is laminated on the laminated gate insulating film (4); and a sixth step wherein the amorphous silicon thin film (5a) is crystallized by radiating a laser beam from above the amorphous silicon thin film (5a).