A chip useful for treating cells and the like which has a mechanism and a structure wherein the size of a hole pattern is arbitrarily changed so that cells can easily move in and get out from the hole in scattering or collecting cells but can hardly get out from the hole during washing or antigen-stimulation. The chip comprises a crosslinked product of a temperature-responsive polymer as a constituting member and being provided with a film having a hole pattern on the surface of a baseboard. A method of producing the chip comprises applying a composition containing a crosslinkable temperature-responsive polymer on the surface of a baseboard to thereby form a coating film, crosslinking the coating film to thereby form the crosslinked product as described above and then forming a hole pattern on the coating film of the crosslinked product.