An object of the present invention is to provide a high-purity crystal of a compound represented by formula (1a) that is an activated blood coagulation factor X (FXa) inhibitor. Solution: High-purity crystals of a compound represented by the following formula (1a): wherein, with regard to the content of impurities, the maximum content of any one type of impurity is 0.03% or less, and the total content of impurities is 0.13% or less, and wherein the high-purity crystals are obtained by a step of dissolving crystals in a solvent and then recrystallizing them.
