Provided is a sulfide solid electrolyte material which has a composition that does not contain Ge, while having a smaller Li content than conventional sulfide solid electrolyte materials, and which has both lithium ion conductivity and chemical stability at the same time. A sulfide solid electrolyte which has a crystal structure represented by composition formula (Li3.45+β−4αSnα)(Si0.36Sn0.09)(P0.55−βSiβ)S4 (wherein α≤0.67, β≤0.33 and 0.43