We have studied proton capture reactions on unstable proton-rich nuclei relevant to rapid proton-capture (rp) process using a Coulomb dissociation method. Using this method, three stellar reactions, (22)mg(p, gamma)(23)Al, (26)Si(p, gamma)27(P), and (30)S(p,gamma)(31)Cl were studied at RIKEN Nishina Center. The radiative widths of the first excited state in (23)Al and (27)P, which are relevant to the stellar reactions, were obtained. We discuss the details of the Coulomb dissociation and the astrophysical implications obtained from our studies.