In the event of a collision with the end of a vehicle guardrail, the high rigidity continues to pose a threat to the safety of passengers; hence, an end treatment facility must be mandatorily installed. This requires a shock-absorbing mechanism design to reduce the impact on the occupant and a shock-absorbing structure that can protect the occupant from an abrupt deceleration movement. In this study, the structure of a guardrail was improved. For a head-on collision of a vehicle with an end treatment facility, the impact absorption performance owing to the structure of the guardrail was observed by a simulation using ABAQUS, a finite element analysis program. To improve the impact absorption performance of the end treatment facility, we designed a structure in which a groove is formed in the guardrail, pressed in the longitudinal direction, and then pushed backward according to the groove shape to absorb the impact. The calculation of the reaction force of the collision member according to the guardrail groove shape showed that the wave shape had the lowest reaction force. The actual crash test report also satisfied the absorption performance evaluation with excellent results for the passenger protection performance evaluation criteria (THIV((Theoretical Head Impact Velocity)) 15.7% and PHD (Post-impact Head Deceleration) 21.17%).