The present invention relates to a synchronous motor driving apparatus having a power converter (2) which applies AC variable voltages having variable frequency to a synchronous motor (3) includes a pulsating current application unit (10) for applying pulsating current to the synchronous motor (3) and a magnetic pole position presumption unit (12). The magnetic pole position presumption unit (12) detects two current values ”Idcp1 and ”Idcp2 on the positive side and two current values ”Idcn1 and ”Idcn2 on the negative side of the pulsating current and presumes the magnetic pole position of the synchronous motor (3) on the basis of difference between change rates of ”Idcp1 †’ ”Idcp2 and ”Idcp1 †’ ”Idcp2.
