A phase modulator (100, 200) comprising: a first liquid crystal element in which first liquid crystal material is filled between a pair of substrates facing each other, and a second liquid crystal element in which second liquid crystal material is filled between a pair of substrates facing each other, wherein electrode layers are formed on inner surface of the substrates facing the first liquid crystal material and electrode layers are formed on inner surface of the substrates facing the second liquid crystal material, and wherein: the first liquid crystal element and the second liquid crystal element are arranged so that a light passes through the first liquid crystal element and the second liquid crystal element; in the state in which no voltage is applied between the pair of the electrode layers of the first liquid crystal element nor between the pair of the electrode layers of the second liquid crystal element, the first liquid crystal material shows optical isotropy with a first isotropy refractive index (n iso1) and the second liquid crystal material shows optical isotropy with a second isotropy refractive index (n iso2); in the state in which a predetermined range of voltage is applied both between the pair of the electrode layers of the first liquid crystal element and between the pair of the electrode layers of the second liquid crystal element, the first liquid crystal material shows optically uniaxial anisotropy with a first ordinary refractive index (n o1) and a first extraordinary refractive index (n e1) which is larger than the first ordinary refractive index (n o1), and the second liquid crystal material shows optically uniaxial anisotropy with a second ordinary refractive index (n o2) and a second extraordinary refractive index (n e2) which is smaller than the second ordinary refractive index (n o2); both of the first liquid crystal material and the second liquid crystal material are blue phase liquid crystal material; in the state in which the first liquid crystal material shows optically uniaxial anisotropy, an optic axis of the first liquid crystal material is perpendicular to each substrate of the first liquid crystal element; and in the state in which the second liquid crystal material shows optically uniaxial anisotropy, an optic axis of the second liquid crystal material is perpendicular to each substrate of the second liquid crystal element; and the sum of a value calculated by subtracting the first ordinary refractive index (n o1) from the first isotropy refractive index (n iso1) and a value calculated by subtracting the second ordinary refractive index (n o2) from the second isotropy refractive index (n iso2) has a value other than zero. the first liquid crystal element and the second liquid crystal element are arranged so that a light passes through the first liquid crystal element and the second liquid crystal element; in the state in which no voltage is applied between the pair of the electrode layers of the first liquid crystal element nor between the pair of the electrode layers of the second liquid crystal element, the first liquid crystal material shows optical isotropy with a first isotropy refractive index (n iso1) and the second liquid crystal material shows optical isotropy with a second isotropy refractive index (n iso2); in the state in which a predetermined range of voltage is applied both between the pair of the electrode layers of the first liquid crystal element and between the pair of the electrode layers of the second liquid crystal element, the first liquid crystal material shows optically uniaxial anisotropy with a first ordinary refractive index (n o1) and a first extraordinary refractive index (n e1) which is larger than the first ordinary refractive index (n o1), and the second liquid crystal material shows optically uniaxial anisotropy with a second ordinary refractive index (n o2) and a second extraordinary refractive index (n e2) which is smaller than the second ordinary refractive index (n o2); both of the first liquid crystal material and the second liquid crystal material are blue phase liquid crystal material; in the state in which the first liquid crystal material shows optically uniaxial anisotropy, an optic axis of the first liquid crystal material is perpendicular to each substrate of the first liquid crystal element; and in the state in which the second liquid crystal material shows optically uniaxial anisotropy, an optic axis of the second liquid crystal material is perpendicular to each substrate of the second liquid crystal element; and the sum of a value calculated by subtracting the first ordinary refractive index (n o1) from the first isotropy refractive index (n iso1) and a value calculated by subtracting the second ordinary refractive index (n o2) from the second isotropy refractive index (n iso2) has a value other than zero.