  We propose to use high-energy exclusive reactions for probing internal
structure of exotic hadron candidates. First, the constituent counting rule of
perturbative QCD can be used for finding internal configurations of an exotic
hadron candidate. It is because the number of constituents ($n$), which
participate in the exclusive reaction, is found by the scaling behavior of the
cross section $d\sigma/dt \propto 1/s^{n-2}$ at large momentum transfer, where
$s$ is the center-of-mass energy squared. As an example, we show that the
internal structure of $\Lambda \, (1405)$ should be found, for example, by the
reaction $\pi^- + p \to K^0 + \Lambda (1405)$. Second, the internal structure
of exotic hadron candidates should be investigated by hadron tomography with
generalized parton distributions (GPDs) and generalized distribution amplitudes
(GDAs) in exclusive reactions. Exotic nature should be reflected in the GPDs
which contain two factors, longitudinal parton distributions as indicated by
the constituent counting rule and transverse form factors as suggested by the
hadron size. The GDAs should be investigated by the two-photon process
$\gamma^* \gamma \to h\bar h$, for example $h=f_0$ or $a_0$, in
electron-positron annihilation. Since the GDAs contain information on a
time-like form factor, exotic nature should be found by studying the $h\bar h$
invariant mass dependence of the cross section. The internal structure of
exotic hadron candidates should be clarified by the exclusive reactions at
facilities such as J-PARC and KEKB.
