We present low-loss microscope optics using an axicon-based beam shaper, which can convert a Gaussian beam to a ring beam to minimize the optical loss from blocking by the back aperture of the objective lens while maintaining spatial resolution. To design the beam shaper, we characterize the position-dependent transmittance of high-transmittance objective lenses and numerically calculate the beam propagation in the beam shaper. We also clarify the effect of misalignments of the beam shaper and wavefront distortion of the input beam. Furthermore, we experimentally demonstrate a low-loss microscope optical system with a high transmittance of 86.6% and high spatial resolution using the full numerical aperture of the objective lenses.