In order to elucidate the relationship between the electrical properties and composition (d and x) of La1-xSrxMnO3+d, precise measurements were made on the conductivity, sigma and Seebeck coefficient, Q, for the oxide with 0 less than or equal to x less than or equal to 0.7 as a function of T and P(O-2) up to 1273 K. Analysis was made for the high-temperature paramagnetic state using the nonstoichiometry data and defect and electronic structure models reported by the present authors. It was shown that sigma and Q in the oxygen excess La1-xSrxMnO3+d (d > 0) are fixed to the value at those of the stoichiometric oxygen content, d = 0. In the oxygen deficient La1-xSrxMnO3+d, they are essentially determined by the mean Mn valence and temperature. The predominant electrical conduction was found to take place by the electron hopping on the e(g)up arrow level of Mn. In La1-xSrxMnO3+d (d less than or equal to 0) under the condition of z = x + 2d less than or equal to 1/3, sigma is given by: sigma = (2.8 x 10(6)/T){2 (-z(2) - z + 6)(6 -18z)/(17 - z)(2) + (-z(2) - z + 6) (z(2) + 18z + 5)/(17 -z)(2)} exp{(-Ea/(kT)} where the activation energy Ea = - 0.59(3 + z) + 2.00 eV. For z greater than or equal to 1/3, it is given by: sigma = (2.8 x 10(6)/T) z(1 - z) exp{(-Ea/(kT)} where Ea = -0.036(3 + z) + 0.16 eV. Q is also described essentially by this model. However, the effect of minority carrier conduction is clearly found in Q in addition to the major conduction on e(g)up arrow level. The major carrier conduction is p-type and the minor carrier is n-type for z less than or equal to 0.5 and vice versa for z greater than or equal to 0.5.