To provide a medical instrument and a medical material using an aliphatic polyester resin composition which show little change in weight average molecular weight during sterilization by ionizing radiation.

The ionizing radiation sterilized medical instrument and the medical material include an aliphatic polyester resin and an aromatic compound condensation product having one or more hydroxyl groups and one or more carboxyl groups at 0.1-30 wt.% with respect to the resin. In particular, the aliphatic polyester resin is selected from a group of polycaprolactone, polytrimethylene carbonate, polydioxanone, a copolymer thereof, a polymer blend thereof and a polymer alloy thereof.