  It is clear that matter is dominant in the Universe compared to antimatter.
We call this problem baryon asymmetry. The baryon asymmetry is experimentally
determined by both cosmic microwave background and big bang nucleosynthesis
measurements. To resolve the baryon number asymmetry of the Universe as well as
neutrino oscillations, we study a radiative seesaw model in a modular $A_4$
symmetry. Degenerate heavy Majorana neutrino masses can be naturally realized
in an appropriate assignments under modular $A_4$ with large imaginary part of
modulus $\tau$, and it can induce measured baryon number via resonant
leptogenesis that is valid in around TeV scale energy theory. We also find that
the dominant contribution to the CP asymmetry arises from Re[$\tau$] through
our numerical analysis satisfying the neutrino oscillation data.
