  We investigate the pressure effect on the layered Dirac fermion system, which
is realized in quasi-two-dimensional organic compound {\alpha}-(BEDT-TTF)2I3.
The trajectory of the contact points is investigated using the tight-binding
model with the transfer integrals determined by X-ray diffraction experiments.
Vanishing of the Dirac fermion spectrum, opening of the gap, and pressure
dependence of inter-layer magnetoresistance are discussed.
