Substrate of cell culture container, and cell culture container

A substrate of a cell culture container, having a bottom face and a surface provided on the opposite side from the bottom face, wherein

• the surface has a dent-formed region having a plurality of dents formed,
• an average depth of the plurality of dents is 200 μm or more,
• the plurality of dents includes a first dent and a second dent adjacent to each other,
• a nodal line of a cut surface of the substrate which passes the center of an opening of the first dent and the center of an opening of the second dent, and the first dent, has a first curved line which rises from the bottom of the first dent and extends as curved toward the second dent,
• the nodal line of the cut surface and the second dent has a second curved line which rises from the bottom of the second dent and extends as curved toward the first dent,
• the first curved line and the second curved line are connected at a connecting point,
• the following formula (1) is satisfied wherein θ1 (deg) is an angle formed by a first tangent line which passes the connecting point and which is in contact with the first curved line, and a base line which passes the connecting point and which is in parallel with the bottom face, and n is a refractive index of the substrate to light having a wavelength of 540 nm, and
• the following formula (2) is satisfied wherein θ2 (deg) is an angle formed by a second tangent line which passes the connecting point and which is in contact with the second curved line, and the base line:
• θ1<90−θ2+sin−1{sin(θ2)×1.38/n} formula (1)
• θ2<90−θ1+sin−1{sin(θ1)×1.38/n} formula (2).