Provided are sulfide solid electrolyte particles which have sufficient ion conductivity and which are configured to suppress hydrogen sulfide generation, and an all-solid-state battery comprising the sulfide solid electrolyte particles. Disclosed are sulfide solid electrolyte particles comprising Li, P, S and a halogen as constituent elements and having a Li/P molar ratio of more than 3, wherein an oxygen/sulfur element ratio of a particle surface measured by XPS is 0.29 or more and 0.81 and less, and an oxygen/sulfur element ratio at a depth of 30 nm (in terms of a SiO2 sputter rate) from the particle surface measured by XPS, is 0.29 or less.