0+, 1-, 2+, and 3- excitations of 28Si are investigated via proton and α inelastic scattering off 28Si. The structure calculation of 28Si is performed with the energy variation after total angular momentum and parity projections in the framework of antisymmetrized molecular dynamics (AMD). As a result of the AMD calculation, the oblate ground and prolate bands, 0+ and 3- excitations, and the 1- and 3- states of the Kπ=0- band are obtained. Using the matter and transition densities of 28Si obtained by AMD, microscopic coupled-channels calculations of proton and α scattering off 28Si are performed. The proton-28Si potentials in the reaction calculation are microscopically derived by folding the Melbourne g -matrix N N interaction with the AMD densities of 28Si. The α -28Si potentials are obtained by folding the nucleon-28Si potentials with an α density. The calculation reasonably reproduces the observed elastic and inelastic cross sections of proton and α scattering. Transition properties are discussed by combining the reaction analysis of proton and α scattering and structure features such as transition strengths and form factors. The isoscalar monopole and dipole transitions are focused.