To provide a biodegradable adhesive which shows a sufficient initial adhesion force against an adherend, does not come off from the adherend after it is attached and is excellent in adhesion property against a surface substrate, and a pressure-sensitive adhesive label using the same.

The biodegradable adhesive contains an aliphatic polyester resin (A) obtained by reacting lactic acid as a main material and a rosin or a rosin derivative (B), wherein the molar ratio (L/D) of L-lactic acid to D-lactic acid contained in the lactic acid is 1-9, the number average molecular weight of the aliphatic polyester resin (A) is 10,000-120,000 and the Tg is from -5 to -60°C.