  On 2004 December 27, a giant flare from the soft gamma repeater 1806$-$20 was
observed. The radiation mechanism of the initial peak of the flare would be
controversial. In this letter we point out that very high-energy cosmic rays
would be produced in the case that the flare was caused by internal shocks, as
is usually considered for gamma-ray bursts. The highest energy of cosmic rays
can reach $10^{19}$ eV, if the Lorentz factor of the shocks is sufficiently
high. Future observations of cosmic rays will inform us about the mechanism of
the giant flare.
