An object of the present invention is to provide a cellulose acetate composition for thermoforming with excellent biodegradability and excellent thermoformability. A cellulose acetate composition for thermoforming containing a cellulose acetate and a glycerin ester-based plasticizer, wherein the cellulose acetate has a degree of acetyl substitution of 1.4 or greater and 2.0 or less, a compositional distribution index (CDI) of 4.0 or less, and a total sulfur content of 15 mg/kg or greater and less than 150 mg/kg.