Comprehensive analyses of the 115In-NQR spectra employing a magnetic dipolar model and a transferred hyperfine model are performed to determine the magnetic structures of Ce3PtIn11. Based on this analysis, we confirmed that the magnetic moment at the Ce(1) site is very small (∼ 4% of that at the Ce(2) site) but finite. Further, for T N2 < T < T N1 and T < T N2, the magnetic moments at the Ce(1) and Ce(2) sites are parallel to the c-axis, and the in-plane propagation vectors in the two Ce atoms sublattices are (qa, qb ) = (1/2, 1/2). In the temperature interval T N2 <T < T N1, for example, both of them have a form of q = (1/2, 1/2, 0). For T < T N2, the magnetic structure in the Ce(2) sublattice is defined by the propagation vector q = (1/2, 1/2, 1/2 or 0), whereas the Ce(1) sublattice forms a six-fold period structure given by q = (1/2, 1/2, 1/6).