According to one embodiment, a rotor includes a shaft and a rotor core. A plurality of flux barriers are formed at the rotor core. The flux barrier has a plurality of bridges, and one or more barrier regions. When a width of the bridge of a first flux barrier is defined as wa, a width of the bridge of a second flux barrier is defined as wb, a value obtained by dividing a radius of a smallest circle that is tangent to a central line of the first flux barrier by an outer radius of the rotor core is defined as a, and a value obtained by dividing a radius of a smallest circle that is tangent to a central line of the second flux barrier by the outer radius of the rotor core is defined as b, and when f(x)=(1−x{circumflex over ( )}2){circumflex over ( )}(3/2) and g(x)=(1−x{circumflex over ( )}3), a relationship of f(b)/f(a)≤wb/wa≤g(b)/g(a) is satisfied.