A beam splitting device includes a phase modulating device which provides a phase difference between a first polarization component and second polarization component of incident light that have mutually perpendicular planes of polarization, and at least one birefringent lens which splits the light passed through the phase modulating device into a first beam having the first polarization component and a second beam having the second polarization component, and which causes the first beam and the second beam to emerge along a common optical axis, and converting at least one of the first and second beams into a convergent light. The phase modulating device includes a liquid crystal layer which is aligned so that long axes of liquid crystal molecules are oriented in the first direction, and two transparent electrodes which are disposed opposite each other by sandwiching the liquid crystal layer therebetween, and the phase modulating device causes a phase difference proportional to a voltage applied between the two transparent electrodes to occur between the first polarization component and the second polarization component.