To provide a tool holding method capable of minimizing the number of spare tools and reducing tool storage place even in the case of deviation between the axis of rotation of a main shaft and the axis of a tool holding part, or between the axis of a shaft part and the axis of a cutting part in a tool, and provide a machining apparatus.

A stationary fixed post 31 and a rotating post 32 freely rotating round the axis P are disposed on a table 2. The tool 16 is held on the main shaft 19, run-out of the cutting part 16c in making one rotation of the main shaft 19 is measured. When the measured value exceeds an allowable value, the tool 16 is placed on the rotating post 32, and only the tool 16 is turned in a designated angle θ round the axis P. After the tool 16 is once held on the main shaft 19, the run-out of the cutting part 16c is measured. This operation is repeated until the run-out of the cutting part 16c becomes the allowable value or less, or the frequency of changing the position of the tool 16 to the main shaft 19 reaches a predetermined frequency.