1. A preamble generating device that generates a preamble constituting a preamble sequence positioned at a beginning of a transmit signal, comprising: a model determiner that determines on a preamble model, the preamble model being an arrangement of 0 and 1 data according to a predetermined criterion; a first calculator that reorders elements in at least one of either a real data sequence that is a real part of a data sequence, the data sequence being an arrangement of data of a same number as a number of elements in the preamble model, or an imaginary data sequence that is an imaginary part of the data sequence, and generates first computational data by multiplying each element in a result obtained by applying a fast Fourier transform to data that takes as a real part and an imaginary part thereof at least one of the real data sequence and the imaginary data sequence with reordered elements by an element of the preamble model at a same position as the each element; a second calculator that generates second computational data by applying an inverse fast Fourier transform to the first computational data, and performing computation that converts an absolute value of each element in the inverse fast Fourier-transformed first computational data into a value in a predetermined range; a third calculator that generates third computational data by applying a fast Fourier transform to the second computational data, and multiplying each element in the fast Fourier-transformed second computational data by an element of the preamble model at a same position as the each element; and a decider that applies an inverse fast Fourier transform to the third computational data, computes a peak-to-average power ratio of the inverse fast Fourier-transformed third computational data, and in a case of the peak-to-average power ratio matching a predetermined criterion, generates the third computational data as the preamble.