A spectroscopic study of C-17 was performed via the one-neutron knockout reaction of C-18 on a carbon target at RIKEN-RIBF. Three unbound states at excitation energies of 2.66(2), 3.16(5), and 3.97(3) MeV (preliminary) were observed. The energies are compared with shell-model calculations and existing measurements to deduce their spin-parities. From the comparison, the states at 2.66(2) and 3.97(3) MeV are suggested to be 1/2-and 3/2-, respectively. From its decay property, the state at 3.16(5) MeV is indicated to be 9/2(+).