The present invention provides a fine cellulose fiber sheet, of which various properties and functions such as paper making ability, solvent resistance, adhesion, functionalization agent immobilization, surface zeta potential, hydrophilicity, hydrophobicity, and air permeation resistance are finely controlled, through a process having low environmental impact. A fine cellulose fiber sheet according to the present invention fulfills all of the following requirements (1) to (3): (1) comprises fine cellulose fibers having an average fiber diameter of 2 nm or greater and 1000 nm or less; (2) the weight ratio of the fine cellulose fibers is 50 wt % or greater and 99 wt % or less; and (3) the block polyisocyanate aggregate content as a weight ratio is 1 to 100 wt % of the weight of the fine cellulose fibers.