PURPOSE: To reduce the fluctuation of basicity in time series in manufacturing sintered ore with a Dwight-Lloyd sintering machine, by estimating the basicity on the basis of the difference between the measured and calculated values of the basicity of the sintered ore.

CONSTITUTION: A calculated value of the basicity can be obtained on the basis of the ratio of total CaO/total SiO2 in raw materials (mixed raw materials) including coke at the time of quarrying out said raw materials. On the other hand, a measured value of the basicity is found at a lapse of, for instance, 4hr after the initiation of the sintering. Hence formula I is realized, wherein t is a time for quarrying out the raw materials, B*(t) and B(t) are calculated and measured values, respectively, of the basicity of the raw materials quarried out at said time, and E(t) is the deviation between both of said values. Since data on the basicity of the raw materials quarried out at a time of 4 or more hr ago are known at the present time, time series data E(t-l) corresponding to a retroactive time l(hr) with the proviso of l≥4 is obtained. Said data have correlativity with E(t) even in case of relatively large l, and a correlative coefficient is gradually decreased with the increase of l. Hereon, formula II (wherein S is the coefficient of said gradual decrease) for estimation of the deviation is supposed to estimate the basicity with it.