To provide a thermal displacement correction method and a thermal displacement correction device of machine tool, calculating a thermal displacement on the basis of a rotational frequency of a spindle to eliminate the need of conducting special complicated processing when the rotational frequency of the spindle changes, and the need of individually grasping a heat generation phenomenon and decrease in heat radiation, and properly estimate thermal displacement even if the rotational frequency of the spindle changes, so that thermal displacement can be corrected properly.

CPU 110 computes a thermal displacement Sn of the spindle of the machine tool by an expression based on a response surface methodology: Sn=b1*Sn-1+b2*ω+b3*ω2+b4+ω3+b5*Sn-1*ω(wherein Sn-1 is an estimated thermal displacement, ω is the rotational frequency of the spindle, b1 to 5 is a factor, and the sign * indicates multiplication). A position control command of a moving table moved in the direction of Z axis parallel to the spindle is corrected taking the above thermal displacement as a correction amount.