||Disclosed is a technique for culturing a hepatocyte three-dimensionally to form a spheroid readily. Also disclosed is a technique for forming a spheroid in which a transporter MRP2 (which is a transporter involved in the bile duct excretion) can be highly expressed compared with conventional techniques. The conditions under which a hepatocyte can be formed into a spheroid on a nanopillar (NP) sheet readily, specifically the conditions relating to the temperature of type-I collagen to be applied on the NP sheet, are now found. In addition, the conditions under which the expression level of a gene involved in the excretion of the formed spheroid can be increased are also found. Specifically, a spheroid is formed in advance, and a biological matrix is subsequently overlaid on the spheroid.