Various eVTOLs using multi propellers mounted on front of or behind the wings are being developed. In these eVTOLs, the estimation of the unsteady aerodynamic forces generated by the interaction between the propellers and the wings is one of the important problems. NASA X-57 Maxwell also mounts small multi propellers in front of the wing and two large cruse propellers are installed on the wing tips. These wing tip propellers reduce induced drag of the main wing by suppressing the wing tip trailing vortices. In this study, the calculation method based on unsteady lifting line theory including the effect of the shed vortices, which is able to treat the propeller-wing interaction is developed. We applied this method to the wing tip propellers of X-57 Maxwell and evaluated the unsteady aerodynamic forces obtained by this method.