To provide a novel cellulose compound preferable for an optical film, a cellulose composition with less retardation variation by humidity and a small photoelasticity constant using the cellulose compound, and a cellulose film.

The cellulose compound satisfies the following formulae (1)-(3): formula (1): 1.5A+B3, formula (2): 0A3, and formula (3): 0B3. In the formulae, A represents a substitution degree of a group represented by -C(=O)-L-S-R1 relative to a hydrogen atom constituting a hydroxyl group of cellulose. L represents a divalent connection group and the number of the atom constituting a main chain of the connection group (provided that the hydrogen atom bonded to the atom constituting the main chain and the number of the atom of the substituent are excepted) is 1-10. S represents a sulfur atom. R1 represents a 1-30C alkyl group. B represents a substitution degree of a 2-10C aliphatic acyl group relative to the hydrogen atom constituting the hydroxyl group of the cellulose.