PURPOSE: To reproduce an embroidery pattern in high quality on an embroidery cloth at a high speed by changing embroidery data at the needle center corresponding to a curved part having a slight swinging width into those of a needle location point and carrying out the computing.

CONSTITUTION: This apparatus for changing data for a zigzag embroidery machine with rotation is capable of judging whether a rotational angle (Δθ) of data read for each needle is above a prescribed angle (α) or not, simultaneously judging whether a swinging width (W) is below a prescribed width (β) or not, successively searching for continuous embroidery data for (γ) number of needles including the data when the embroidery data satisfying the rotational angle and swinging width are present, judging the embroidery data for the (c) needles to correspond to a curved embroidery part with a slight swinging width when any of the successively searched embroidery data for the (c) needles is the rotational angle (Δθ) above the prescribed angle (α) and the swinging width (W) below the prescribed swinging width (β), thereby transferring the processing to step 15, collectively changing the embroidery data to the [(c)-1]-th needle at that time from the data at the needle center into those of the needle location point, carrying out the computing, then adding the rotational angle (Δθ) of data for the (c) needles thereto in step 16 and updating the total angle (ΣΔθ) at that time as the rotational angle (Δθ) of the embroidery data for the (c)-th needle in step 17.