When dynamic torques are Ts, Ti, and T2, respectively, and rotation angle speeds are Rs, R1, and R2, respectively, at the time of rotations of the developing sleeve 40 and the screws 41 and 42, the mass of the developer housed in the second agitating chamber 902 is M2, the mass of the developer which is present in the space of the side of the developing sleeve when a space formed by the developing chamber 900 and the first agitating chamber 901 is divided is Ms, the mass of the developer which is present in the space of the side of the screw 41 is M1, gravitational acceleration is G, each load on the developer by rotations of the developing sleeve and the screws is defined as Wds (mW/g)=Rs×Ts×G/Ms, Wd1(mW/g)=R1×T1×G/M1, and Wd2 (mW/g)=R2×T2×G/M2, respectively, relationships of 0.5