PURPOSE: To eliminate a problem of environmental pollution by decomposing an oral cavity inside cleaning tool using biodegradable thermoplastic resin in a short time even when it is thrown away in the ground in abandonment after the use.

CONSTITUTION: In this biodegradable oral cavity inside cleaning tool which is composed of a filament and/or a product material composed of a polymer or a coploymer of one or two or more kinds selected from lactic acid, glycol acid or caprolactone and is formed of biodegradable thermoplastic synthetic resin, when a plasticizer such as citric acid ester or lactic acid ester is blended thereto, moldability is improved. A dental froth and dental froth pick are particularly preferable as the biodegradable oral cavity inside cleaning tool. Thereby, since an equipment and a metal mold in the present condition can be used, this biodegradable oral cavity inside cleaning tool can be inexpensivly produced. Since it is decomposed in a short time even when it is thrown away in the ground in abandonment after use, a problem of environmental pollution is not caused.