To provide a biodegradable multilayer film sheet having a good moldability, excellent lateral and longitudinal tensile strengths and fast decomposition speed.

The biodegradable multilayer film sheet comprises a layer (A) made of a biodegradable polyester resin composition obtained by mixing 100 pts.wt. of an aliphatic polyester resin and 1 to 200 pts.wt. of a polycaprolactone, and a layer (B) made of a composition containing a radiation treated lactone resin and other biodegradable resin in a structure in which the layer (A) is sandwiched between the two layers (A).