A four-wheeled walker is a valuable tool for elderly and disabled persons in activities on daily living. This study investigates a relationship between a handgrip height of the walker and muscular load on a lower limb during steady walking. An elderly subject pushes the walker with variable handgrip height of 0.6m, 0.8m, 1.0m, and 1.2m. Muscular load during walking is estimated by surface electromyogram (EMG) measured from four muscles in the lower limb: the quadriceps femoris, the hamstrings, the tibialis anterior, and the triceps surae. Muscular load is quantified by a root mean square (rms) value of EMG during one stride. The regression analysis between the handgrip height and the rms value shows that the lower handgrip height reduces muscular load in the quadriceps femoris and the tibialis anterior. However, it induces stronger force of the hamstrings for postural control to support a stooping posture of the upper body.