A highly hydrophilic surface, with a water contact angle smaller than 20 degrees, was rendered to a poly-methylmethacrylate [PMMA] by Xe2 excimer lamplight and plasma treatment. In result, the implant material that was highly biocompatible and adhesive to soft tissue was developed. The PMMA surface, which had been pretreated by ammonia plasma, was irradiated with Xe2 excimer lamplight in the presence of hydrazine as a reaction solution. In order to evaluate the wettability of the modified sample, the contact angle with water was measured. The contact angle was decreased from 83 degrees for untreated PMMA to 60 degrees when irradiated the Xe2 lamplight for 30 minutes. With the ammonia plasma pretreatment, the contact angle of the treated sample became to 7 degrees at the 1 minute Xe2 lamp irradiation.