A liquid crystal compound satisfies at least one of physical properties such as a high stability to heat, light and so forth, a high clearing point, a low minimum temperature of a liquid crystal phase, a small viscosity, a suitable optical anisotropy, a large negative dielectric anisotropy, a suitable elastic constant and an excellent compatibility with other liquid crystal compounds.The compound is represented by formula (1).In the formula, for example, R1 and R2 are alkyl having 1 to 15 carbons; ring A1 and ring A2 are 1,4-cyclohexylene or 1,4-phenylene, Z1 and Z2 are a single bond, —(CH2)2—, —CH═CH—, —C≡C—, —COO—, —OCO—, —CH2O—, —OCH2—, —CF2O—, —OCF2— or —CF═CF—, a and b are 0, 1 or 2, and a sum of a and b is 1 or 2.