It is an object of the present invention to provide an ultrafine cellulose fiber-containing sheet that is excellent in terms of weather resistance. The present invention relates to a sheet comprising cellulose fibers having a fiber width of 1000 nm or less, wherein the cellulose fibers have anionic functional groups, and the YI increase percentage calculated according to the following equation is 1500% or less. YI increase percentage (%)=(yellowness of the sheet after heating−yellowness of the sheet before heating)/yellowness of the sheet before heating×100, wherein the yellowness of the sheet after heating is a yellowness measured in accordance with JIS K 7373, after the sheet is subjected to hot pressing at 180° C. at 0.5 MPa for 1 minute, whereas the yellowness of the sheet before heating is a yellowness measured in accordance with JIS K 7373, before the sheet is subjected to the hot pressing.