This book presents proton-³He elastic scattering experiments conducted at intermediate energies, with the aim of identifying three-nucleon force (3NF) effects in a four-nucleon scattering system. The 3NF plays an essential part in understanding various nuclear phenomena, and few-nucleon scatterings further offers a good opportunity to study the dynamical aspects of 3NFs. In particular, proton-³He scattering is one of the most promising approaches to an iso-spin dependence of 3NFs. The book in-depth explains the achieved development of polarized ³He target system for the proton-³He scattering experiments, and describes successful precise evaluation of the target polarization. The experiments yielded the first precise data for this system and offer a valuable resource for the study of 3NFs.