The purpose of this chapter of nonlinear theory of elementary particles (NTEP) is to describe the mechanism of generation of massive elementary particles. The theory, presented below, indicates the possibility of the particle mass production by means of massive intermediate boson, but without the presence of Higgs's boson. It is shown that nonlinearity is critical for the appearance of particles' masses. PASC: 11.10.Lm, 12.10.En Keywords: nonlinear theory, intermediate boson, nonlinear equation, mass origin, Higgs mechanism 1.0. The postulate of generation of massive elementary particles The purpose of this chapter is to describe the mechanism of generation of massive elementary particles on the basis of the hypotheses, accepted in the chapter (Kyriakos, 2010a). Here, the mass-free particle, the photon, i.e. a quantum of an electromagnetic field, serves as a "billet" for the generation of a massive particle. In this case, the appearance of the mass of a particle is identical to the generation of the massive particle itself. There is a mechanism in the theory of Standard Model (SM) that ensures the generation of currents of elementary particles. This mechanism is known as the gauge (or phase) transformation of particles' field (let's recall that the particle's field in QFT is the particle's wave function). In the SM there is also a mechanism that ensures the generation of masses of elementary particles. Here, all particles do not have a mass at the initial stage. In the SM, the mass-free particles acquire mass because of the spontaneous breakdown of the gauge symmetry of vacuum. This mechanism is called Higgs's mechanism. In the framework of axiomatic nonlinear elementary particle theory we accepted (see (Kyriakos, 2010a)) the following basic postulates, which ensure the generation of massive particles: 1) In the proposed theory, in contrast to SM, only a quantum of an electromagnetic wave (photon) does not have mass. 2) The fields of an electromagnetic wave quantum (photon) can under specified conditions undergo a rotation transformation and initial symmetry breaking, which generate different massive elementary particles. It follows from these hypothesis that the equations of elementary particles must be nonlinear modifications of the equations of quantized electromagnetic (EM) waves. The detailed analysis presented in the following chapters shows that because of the rotation transformation and different types of symmetry breaking of the initial photon, such elementary particles can have mass, electric charge, spin (which is a multiple of 1 and ½), helicity, chirality, and all other characteristics of existing elementary particles.