In this study, the concept of autonomous mobility is applied to a gait support mobile robot. The aim of the development of the service robot is to assist the elderly with gait assistant. This study proposes an ergonomic service robot design parameter. The gait assistant path pattern is derived from analysis of the elderly gait. A lever is installed in the AMR in order to measure both the pulling force and the leading force of the elderly. The path generation of the mobile robot is developed through consideration and analysis of elderly gait patterns. The ergonomic design parameters (dimensions, action scope and working space) are determined based on moving scope of the elderly. The gait assistant mobile robot was offered the elderly guide service and Internet service based on the ergonomic design parameters.