A communication device for handling a Peak-to-Average Power Ratio (PAPR), includes a transforming module, configured to perform a first plurality of inverse fast Fourier transforms (IFFTs) on a plurality of coefficients in a scene according to a first inverse fast Fourier transform (IFFT) size and the scene, to obtain a plurality of results; a processing module, coupled to the transforming module, configured to obtain a plurality of norms of the plurality of results, and to obtain a plurality of values of the plurality of coefficients; and a transmitting module, coupled to the processing module, configured to perform a second plurality of IFFTs on a plurality of frequency-domain signals according to a second IFFT size, the plurality of coefficients with the plurality of values and the scene, to obtain a plurality of time-domain signals, wherein the second IFFT size is greater than the first IFFT size.