Nuclear weak processes are investigated based on new shell model Hamiltonians, which give successful description of spin responses in nuclei, and applied to astrophysical problems. Neutrino-induced reactions on 12 C and synthesis of light elements by supernova neutrinos, and effects of contamination of 13 C, whose natural isotopic abundance is 1.1%, on inclusive ν-12 C reactions are discussed. Spin-dipole transitions and ν-induced reactions on 16 O are studied by using a new Hamiltonian with

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... Hamiltonian with proper tensor components, and compared with conventional calculations and previous CRPA results. Gamow-Teller transition strength in 40 Ar and ν-induced reactions on 40 Ar by solar neutrinos are studied based on monopolebased-universal interaction (VMU). We finally discuss electron capture reactions on Ni isotopes in stellar environments. Neutrino-Nucleus Reactions in Carbon and Oxygen Neutrino-induced Reaction on 12 C and Light Element Synthesis Neutrino-induced reactions in p-shell nuclei are investigated based on new shell model Hamiltonians[1], which take into account important roles of tensor interaction properly[9] and give good account of spin-dependent modes in p-shell nuclei. Magnetic moments of p-shell nuclei are systematically well described, and Gamow-Teller (GT) transition strengths in 12 C and 14 C are also well explained [1] . The GT strength in 12 C is enhanced for the new Hamiltonian, SFO[1], compared to conventional Hamiltonians, and the cross sections of ν-induced exclusive charge-exchamge