A synchronous machine controller includes a position detecting unit that detects a position of a rotor, a current detecting unit that detects an armature current, a current command generating unit that generates first and second current commands, a voltage command generating unit that generates a voltage command on the basis of the current commands, the position of the rotor, and the armature current, a power converting unit that outputs a voltage to the synchronous machine on the basis of the voltage command, a magnetic flux estimating unit that estimates an armature interlinkage flux on the basis of a rotational velocity calculated from a variation of the position of the rotor, the voltage command, and the armature current, and a magnet state estimating unit that estimates a magnetic flux or a temperature of the permanent magnet from the position of the rotor, the armature current, and the armature interlinkage flux.