Porous silicon particles and complex porous silicon particles suitable for negative electrode materials etc. for lithium-ion batteries, which achieve high capacity and good cycling characteristics, are provided. Porous silicon particles formed by the joining of a plurality of silicon microparticles, and having an average particle diameter of 0.1 μm to 1000 μm, a three-dimensional network structure having continuous gaps, an average porosity of 15 to 93%, and a structure in which the particles of a whole particle are uniform. Complex porous silicon particles formed by the joining of a plurality of silicon microparticles and a plurality of silicon compound particles, and characterized by containing a compound of silicon and composite elements, having an average particle diameter of 0.1 μm to 1000 μm, and having a three-dimensional network structure having continuous gaps.