  We study the supersymmetric Q balls which decay at present and find that they
create a distinctive spectrum of gamma rays at around O(10) MeV. The charge of
the Q ball is lepton numbers in order for the lifetime to be as long as the
present age of the universe, and the main decay products are light leptons.
However, as the charge of the Q ball decreases, the decay channel into pions
becomes kinematically allowed towards the end of the decay, and the pions are
produced at rest. Immediately, $\pi^0$ decays into two photons with the energy
of 67.5 MeV, half the pion mass, which exhibits a unique emission line. In
addition, $\pi^\pm$ decay into $\mu^\pm$, which further decay with emitting
internal bremsstrahlung, whose spectrum has a sharp cutoff at $\sim$50 MeV. If
the observations would find these peculiar features of the gamma-ray spectrum
in the future, it could be a smoking gun of the supersymmetric Q-ball decay at
present.
