To provide a method for producing a cylinder block, in the case a cylinder block of a closed deck type is produced by die casting molding, where the problem that the insert member to be inserted is deformed by casting pressure is solved, further, deterioration in the fluidity of molten metal is suppressed, and further, the cooling efficiency of molten metal is improved, thus a cylinder block having high strength can be produced.

An insert member 10 for forming a water jacket circulating cooling water, a first filler whose temperature is increased to the first prescribed one, a first filler feeding means 66 feeding the first filler to the inside of the insert member, and a die for cylinder block casting are used. The insert member is arranged at the inside of the cavity of the die, the first filler is fed to the inside of the insert member by the first filler feeding means, and molten metal is poured into the cavity so as to cast a cylinder block body 1.