Provided are: a fine cellulose fiber that is superior in handling properties and that can suitably be used as a reinforcing material or the like for resin; a production method of the fine cellulose fiber; and a slurry and a composite comprising the fine cellulose fibers. The present invention pertains to fine cellulose fibers comprising a carbamate group. The degree of substitution with the carbamate group with respect to hydroxy groups in the fine cellulose fibers is preferably no less than 0.05 and no greater than 0.5. The present invention pertains to a slurry comprising the fine cellulose fibers, to a composite comprising the fine cellulose fibers and a resin, and to a production method of the fine cellulose fibers, comprising performing a heat treatment on a mixture of a plant raw material and urea or the like, and performing a miniaturization treatment of the plant raw material.