Provided are a technique for easily forming a spheroid by three-dimensionally culturing hepatocytes, and a technique for forming a spheroid having a higher expression level of a transporter MRP2 playing a role of biliary excretion than that of a conventional method. In order to solve the above-described problems, the present inventors have found out a condition under which hepatocytes easily form the spheroid on a nanopillar sheet. More specifically, this is related to a concentration of Type I collagen coated onto the NP sheet. Also, they have found out a condition under which an expression level of a gene related to the excretion of the formed spheroid is improved. More specifically, after the spheroid is previously formed, a biological matrix is overlayered thereon.