In drug discovery, it is very important to evaluate liver cells within an organism. Compared to 2D culture methods, the development of 3D culture techniques for liver cells has been successful in maintaining long-term liver functionality with the formation of a hepatic-specific structure. The key to performing drug testing is the establishment of a stable in vitro evaluation system. In this article, we report a Tapered Stencil for Cluster Culture (TASCL) device developed to create liver spheroids in vitro. The TASCL device will be applied as a toxicity evaluation system for drug discovery. The TASCL device was created with an overall size of 10 mm × 10 mm, containing 400 microwells with a top aperture (500 µm × 500 µm) and a bottom aperture (300 µm diameter circular) per microwell. We evaluated the formation, recovery, and size of HepG2 spheroids in the TASCL device. The formation and recovery were both nearly 100%, and the size of the HepG2 spheroids increased with an increase in the initial cell seeding density. There were no significant differences in the sizes of the spheroids among the microwells. In addition, the HepG2 spheroids obtained using the TASCL device were alive and produced albumin. The morphology of the HepG2 spheroids was investigated using FE-SEM. The spheroids in the microwells exhibited perfectly spherical aggregation. In this report, by adjusting the size of the microwells of the TASCL device, uniform HepG2 spheroids were created, and the device facilitated more precise measurements of the liver function per HepG2 spheroid. Our TASCL device will be useful for application as a toxicity evaluation system for drug testing.