Various aspects of plasma diagnostics for magnetic-confinement fusion reactors and material processing by the aid of laser techniques, were discussed and reviewed. The outline of 'System for Laser-aided Plasma Diagnostics', which was recently being equipped in Kyushu University, was de-scribed, and our research projects on the following two items were introduced: 1) novel techniques on the Thomson scattering to determine the electron and ion temperatures, and 2) particle measurement in plasmas by the application of laser spectroscopy. Laser spectroscopy made the determination of following parameters possible, namely the spatical distribution of the velocity, the temperature, the electric field, and the magnetic field, as well as the density distri-bution of various particles in plasmas.