Electrical conductivity, Seebeck coefficient, and nonstoichiometric oxygen content of La2-xSrxNiO4+δ (x = 0, 0.2, 0.4) were measured as a function of Sr content, temperature, and oxygen partial pressure. At above around 873 K, mobility of hole decreases as temperature increases. The temperature dependence of hole mobility indicates large polaron conduction. The relationship between Seebeck coefficient and electrical conductivity is explained by metal like band conduction model. The behavior of electrical conductivity and Seebeck coefficient strongly suggests that electron (hole) is delocalized in La2-xSrxNiO4+δ at high temperatures.