A determination method of a casting state in continuous casting where there are a solidified shell, a mold flux layer, and a mold being respective thermal conductors between a molten steel and cooling water for the mold, the determination method comprising: a first step of finding a heat transfer coefficient α being a heat flux per a unit temperature difference between the solidified shell and the mold sandwiching the mold flux layer and a heat transfer coefficient β between the molten steel and the solidified shell by using data from a plurality of temperature sensing units which are embedded in the mold while shifting positions in a casting direction by solving an inverse problem, and estimating a solidified shell thickness and a solidified shell temperature from the heat transfer coefficient α and the heat transfer coefficient β; a second step of setting the heat transfer coefficient α, the heat transfer coefficient β, the solidified shell estimated thickness, and the solidified shell estimated temperature found in the first step as solidified state in mold estimation amounts, and obtaining solidified state in mold evaluation amounts from the solidified state in mold estimation amounts; and a third step of determining whether a normal casting state or an abnormal casting state is present by comparing at least one or more kinds of amounts contained in the solidified state in mold estimation amounts and the solidified state in mold evaluation amounts obtained in the second step with allowable limit values which are found based on at least one or more kinds of amounts contained in the solidified state in mold estimation amounts and the solidified state in mold evaluation amounts when the abnormal casting occurred in a past and stored in an allowable limit value storage unit, wherein in the mold where widths in a horizontal direction of two planes which are not adjacent but face each other are equal from among four planes of mold surfaces which are in contact with a cast slab through the mold flux layer, two planes whose widths in the horizontal direction are narrower than the other two planes are called as short sides, a difference of the heat transfer coefficients β obtained at the short sides at the same mold height position is called as a short side β difference, a difference of solidified shell thicknesses obtained at the short sides at the same mold height position is called as a short side shell thickness difference, and the solidified state in mold evaluation amounts are calculated from at least either the short side β difference or the short side shell thickness difference. a first step of finding a heat transfer coefficient α being a heat flux per a unit temperature difference between the solidified shell and the mold sandwiching the mold flux layer and a heat transfer coefficient β between the molten steel and the solidified shell by using data from a plurality of temperature sensing units which are embedded in the mold while shifting positions in a casting direction by solving an inverse problem, and estimating a solidified shell thickness and a solidified shell temperature from the heat transfer coefficient α and the heat transfer coefficient β; a second step of setting the heat transfer coefficient α, the heat transfer coefficient β, the solidified shell estimated thickness, and the solidified shell estimated temperature found in the first step as solidified state in mold estimation amounts, and obtaining solidified state in mold evaluation amounts from the solidified state in mold estimation amounts; and a third step of determining whether a normal casting state or an abnormal casting state is present by comparing at least one or more kinds of amounts contained in the solidified state in mold estimation amounts and the solidified state in mold evaluation amounts obtained in the second step with allowable limit values which are found based on at least one or more kinds of amounts contained in the solidified state in mold estimation amounts and the solidified state in mold evaluation amounts when the abnormal casting occurred in a past and stored in an allowable limit value storage unit, wherein in the mold where widths in a horizontal direction of two planes which are not adjacent but face each other are equal from among four planes of mold surfaces which are in contact with a cast slab through the mold flux layer, two planes whose widths in the horizontal direction are narrower than the other two planes are called as short sides, a difference of the heat transfer coefficients β obtained at the short sides at the same mold height position is called as a short side β difference, a difference of solidified shell thicknesses obtained at the short sides at the same mold height position is called as a short side shell thickness difference, and the solidified state in mold evaluation amounts are calculated from at least either the short side β difference or the short side shell thickness difference.