  In this paper we consider the effects on big bang nucleosynthesis (BBN) of
the hadronic decay of a long-lived massive particle. If high-energy hadrons are
emitted near the BBN epoch ($t \sim 10^{-2}$ -- $10^2 \sec$), they
extraordinarily inter-convert the background nucleons each other even after the
freeze-out time of the neutron to proton ratio. Then, produced light element
abundances are changed, and that may result in a significant discrepancy
between standard BBN and observations. Especially on the theoretical side, now
we can obtain a lot of experimental data of hadrons and simulate the hadronic
decay process executing the numerical code of the hadron fragmentation even in
the high energy region where we have no experimental data. Using the light
element abundances computed in the hadron-injection scenario, we derive a
constraint on properties of such a particle by comparing our theoretical
results with observations.
