  We investigate the photoproduction of the $\Theta^+(1540)$ on a nucleon
($\gamma n \to K^- \Theta^+$, $\gamma p \to \bar{K}^0 \Theta^+$) and the
pion-induced $\Theta^+$ production reaction on the proton ($\pi^- p \to K^-
\Theta^+$). The total cross sections near threshold are estimated by using
hadronic models with effective interaction Lagrangians and form factors that
preserve gauge-invariance of the electromagnetic current. The photoproduction
cross sections are found to be a few hundred nb, with the cross section on the
proton being larger than that on the neutron. The pion-induced production cross
section is found to be around a few hundred $\mu$b but sensitive to the $K^* N
\Theta$ coupling whose value is not yet known. We also study the production
cross section assuming that the $\Theta^+$ has negative parity. The cross
sections are then found to be much suppressed compared to the case where
$\Theta^+$ has positive parity. Hence, the interpretation of the $\Theta^+$ as
an odd-parity pentaquark state seems to be disfavored from the estimates of
cross section for the photon-proton reaction from the SAPHIR experiment.
