Negative electrode active material particles comprise base particles having: a silicate phase containing Li2O, SiO2, at least one oxide selected from M12O3, M2O2, M32O5, and M4O3 (where M1, M2, M3, and M4 are elements other than alkali metals, alkali earth metals, and Si), and a discretionary component MO (where M is an alkali earth metal); and silicon particles dispersed in the silicate phase. The element contents for the elements contained in the silicate phase are: 3-33 mol % of Li; 40-78 mol % of S; and 1-40 mol % of M1, M2, M3, and M4. If MO is contained, the M content in the silicate phase is 1-10 mol %.