To improve insufficient filling of a molten metal in the production of a thin casting 1.

A method for producing a thin casting is provided for inpouring the molten metal into a cavity 40 within a die-casting die and forming a casting with the shape of the cavity, and the method includes: a die preparation step of preparing a die-casting die provided with a main gate part 30C for feeding the molten metal to the cavity, at least one subgate part 30R, 30L for feeding the molten metal to the cavity from the side direction to the flowing direction of the molten material from the main gate part, an overflow part 50 arranged at the side opposite from the main gate part based on the cavity and having a flow passage cross-section larger than that of the other part in the downstream side of the subgate part; and a casting step of inpouring the molten metal from the main gate part and subgate part of the die-casting die to the cavity to form a casting with the shape of the cavity.