PROBLEM TO BE SOLVED: To provide a base plate for forming an aggregate with a controlled outline for adhesion-depending cells, with which base plate culture cells can grow for a long time by mutually giving a foothold by adhering between cells even when the cells flow on a culture liquid. SOLUTION: The base plate 11 is formed of a non-cell adhesive material to which culturing cells do not adhere, and it has dent parts 13 for controlling the outlines of cell aggregates formed by adhering between cells seeded.