A phase modulator includes; a first liquid crystal element and a second liquid crystal element, wherein: in the state in which no voltage is applied to the first liquid crystal element nor to the second liquid crystal element, both of the first liquid crystal material and the second liquid crystal material show optical isotropy; and in the state in which a predetermined range of voltage is applied both to the first liquid crystal element and to the second liquid crystal element, the first liquid crystal material shows optically uniaxial anisotropy with a first ordinary refractive index and a first extraordinary refractive index which is larger than the first ordinary refractive index, and the second liquid crystal material shows optically uniaxial anisotropy with a second ordinary refractive index and a second extraordinary refractive index which is smaller than the second ordinary refractive index.