A method for spraying a chemical solution, comprising: spraying the chemical solution onto a dryer roller (D1-D9) by two nozzle devices disposed at a certain interval there between with the two nozzle devices each reciprocated along a rail extended in the width direction of the dryer roller (D1-D9) in a state that the dryer roller (D1-D9), for guiding wet paper, is being rotated, in a dry part of a paper-making machine, wherein a time T required for the two nozzle devices each to travel one-way is set as 0.2 to 1.5 minutes; a rotational speed Vd of the dryer roller (D1-D9) is set as not less than 100 times/min; a number of contacts N that a point on the dryer roller (D1-D9) surface makes contact with the wet paper during the time T is set as 30 to 250 times; the time T, the rotational speed Vd, and the number of contacts N satisfy the relationship of N=T ∗ Vd; and a total amount of the sprayed chemical solution is set as 0.3 to 500 mg/m 2 as an effective component amounts, a first nozzle device of the two nozzle devices is arranged to reciprocate between a position corresponding to an end of the wet paper and a position corresponding to the center of the wet paper along the rail, and a second nozzle device thereof is arranged to reciprocate between a position corresponding to the other end of the wet paper and a position corresponding to the center of the wet paper along the rail, an average moving speed Vn of the two nozzle devices is each set as 4 to 10 m/min; a paper width W of the wet paper is set as 4 to 12 m; and the average moving speed Vn, the paper width W, and the time T satisfy the relationship of T=W/2Vn, a transportation speed Vp of the wet paper is set as not less than 600 m/min; a diameter D of the dryer roller (D1-D9) is set as 1.50 to 1.85 m; and the rotational speed Vd, the transportation speed Vp, and the diameter D satisfy the relationship of Vd=Vp/πD, the two nozzle devices, having the same construction, are each arranged to spray the chemical solution onto the dryer roller (D1-D9) radially. wherein a time T required for the two nozzle devices each to travel one-way is set as 0.2 to 1.5 minutes; a rotational speed Vd of the dryer roller (D1-D9) is set as not less than 100 times/min; a number of contacts N that a point on the dryer roller (D1-D9) surface makes contact with the wet paper during the time T is set as 30 to 250 times; the time T, the rotational speed Vd, and the number of contacts N satisfy the relationship of N=T ∗ Vd; and a total amount of the sprayed chemical solution is set as 0.3 to 500 mg/m 2 as an effective component amounts, a first nozzle device of the two nozzle devices is arranged to reciprocate between a position corresponding to an end of the wet paper and a position corresponding to the center of the wet paper along the rail, and a second nozzle device thereof is arranged to reciprocate between a position corresponding to the other end of the wet paper and a position corresponding to the center of the wet paper along the rail, an average moving speed Vn of the two nozzle devices is each set as 4 to 10 m/min; a paper width W of the wet paper is set as 4 to 12 m; and the average moving speed Vn, the paper width W, and the time T satisfy the relationship of T=W/2Vn, a transportation speed Vp of the wet paper is set as not less than 600 m/min; a diameter D of the dryer roller (D1-D9) is set as 1.50 to 1.85 m; and the rotational speed Vd, the transportation speed Vp, and the diameter D satisfy the relationship of Vd=Vp/πD, the two nozzle devices, having the same construction, are each arranged to spray the chemical solution onto the dryer roller (D1-D9) radially.