Working posture of human should be predicted so as to simulate physical workload with the digital human modeling (DHM) simulation. The working posture prediction determines the posture by optimizing predetermined objective functions (hereafter referred to as the posture evaluation function; PEF) such as the sum of joint moments. Previous researches proposed PEFs for different working position (or the hand position), but the consideration on the effect of exerted force of human was not enough. The aim of this study was to investigate required PEFs when considering the difference of exerted force. A pushing task in the sagittal plane was used as the case study, and the joint angles were measured as the reference data with different working height, force direction, and force amplitude. First, the weighted sum of the joint moments and joint angles from the neutral posture (the two-indicator model) was applied as the PEF; however, the PEF could not reflect the difference of force direction when the force amplitude was 0 N. The difference between the force direction and the long axis of manipulability ellipsoid was added to the two indicators, and the PEF was revised (the three-indicator model) so as to consider the effect of force direction on the working posture. The threeindicator model improved the prediction accuracy. We concluded that the three-indicator model was appropriate as the PEF for a task with different exerted force.