The purpose of this study was to evaluate the effect of degradation of a denture base resin on bond strength to relining resins. Denture base resin specimens were immersed under various conditions to simulate degradation. Tensile bond strength of denture base resin after immersion to relining resins was measured with or without surface grinding. The bond strength of denture base resin without grinding after immersion to relining resin was significantly lower than that before immersion. However, bond strength was improved by surface grinding before bonding. These results suggest that bonding efficiency of denture base resin to relining resins was affected by immersion condition, which caused potential degradation of the denture base resin.