  In this paper the results of numerical simulation of monolayer graphene in
external magnetic field are presented. The numerical simulation is performed in
the effective lattice field theory with noncompact $3 + 1$-dimensional Abelian
lattice gauge fields and $2 + 1$-dimensional staggered lattice fermions. The
dependences of fermion condensate and graphene conductivity on the dielectric
permittivity of substrate for different values of external magnetic field are
calculated. It is found that magnetic field shifts insulator-semimetal phase
transition to larger values of the dielectric permittivity of substrate. The
phase diagram of graphene in external magnetic field is drawn.
