Provided is a material-fixing substrate that does not have to use copper as a catalyst because the substrate-bonding site includes a cyclic alkyne to form a covalent bond with a surface of the substrate, and therefore that can reduce damage to a cell, for example, in a case where a to-be-fixed material is the cell. The material-fixing substrate has a to-be-fixed material fixed thereon via a material-fixing agent. The material-fixing agent includes: a substrate-bonding site that forms a covalent bond with a surface of the substrate and includes at least a cyclic alkyne; a hydrophilic site that is bonded to the substrate-bonding site; a light-responsive site that is bonded to the hydrophilic site and changes the skeleton thereof by irradiation with light; and an attachment site to which the to-be-fixed material is attached.