We carry out photoproduction experiments using linearly polarized photon beams with energies of 1.5-3 GeV at SPring-8/LEPS. The photoproduction of various mesons and baryons is important to understand hadron production mechanisms. We took the data for the $\gamma p$ $\rightarrow$ $\pi^{-}\Delta^{++}$ and $\gamma p$ $\rightarrow$ $\pi^{+}\Delta^{0}$ reactions at the forward $\pi$ angles of 0.7$<\cos\theta_{\pi}^{c.m.}<$1 with the same acceptance for $\pi^{-}$ and $\pi^{+}$. Precise comparison between the $\bar{u}u$ and $\bar{d}d$ productions in the final state is possible, which is expected to give important information on how hadrons are produced. Preliminary results of photon beam asymmetries, which are sensitive to reaction mechanisms, are reported.