The subject is to provide a liquid crystal compound satisfying at least one of physical properties such as a high stability to heat or light, a high clearing point (or a high maximum temperature), a low minimum temperature of a liquid crystal phase, a small viscosity, a suitable optical anisotropy, a large dielectic anisotropy, a suitable elastic constant and an excellent compatibility with any other liquid crystal compound, a liquid crystal composition including this compound and a liquid crystal display device including this composition. The compound is represented by the following formula (1a): wherein R1 is alkyl having 1 to 15 carbons or the like; ring A1, ring A2, ring A3 and ring A4 are independently 1,4-phenylene, naphthalene-2,6-diyl or the like; Z1 and Z2 are independently a single bond or the like; o and p are independently 0, 1 or 2; and n is an integer from 2 to 10.