A stirrer comprising: a rotor having a plurality of blades, a partition wall for the purpose of holding a discharge pressure of the rotor, and a screen laid around the rotor, all of which are provided concentrically, wherein: the screen comprises a plurality of slits in a circumferential direction thereof and a screen member located between adjacent slits; the rotor and the screen are configured such that, by rotating at least the rotor, a fluid to be processed is discharged as an intermittent jet flow from inside to outside the screen through the plurality of slits; the screen forms a shape having a circular cross-section; an opening of the plurality of slits provided on an inner wall surface of the screen is made to serve as an inflow opening, and an opening of the plurality of slits provided on an outer wall surface of the screen is made to serve as an outflow opening; and a width (So) of the outflow opening in a circumferential direction is set to be narrower than a width (Si) of the inflow opening in a circumferential direction; the plurality of slits of the screen are defined by a front-side end surface and a back-side end surface arranged with a distance therebetween in the rotation direction of the plurality of blades, and at least an area of the front-side end surface of an inflow side of the slit is inclined forward in the rotation direction of the plurality of blades characterized in that an angle of at least the area of the front-side end surface of the inflow side of the slit to a radius passing through a center of the outflow opening in the circumferential direction is in a range of 1 to 45 degrees. a rotor having a plurality of blades, a partition wall for the purpose of holding a discharge pressure of the rotor, and a screen laid around the rotor, all of which are provided concentrically, wherein: the screen comprises a plurality of slits in a circumferential direction thereof and a screen member located between adjacent slits; the rotor and the screen are configured such that, by rotating at least the rotor, a fluid to be processed is discharged as an intermittent jet flow from inside to outside the screen through the plurality of slits; the screen forms a shape having a circular cross-section; an opening of the plurality of slits provided on an inner wall surface of the screen is made to serve as an inflow opening, and an opening of the plurality of slits provided on an outer wall surface of the screen is made to serve as an outflow opening; and a width (So) of the outflow opening in a circumferential direction is set to be narrower than a width (Si) of the inflow opening in a circumferential direction; the plurality of slits of the screen are defined by a front-side end surface and a back-side end surface arranged with a distance therebetween in the rotation direction of the plurality of blades, and at least an area of the front-side end surface of an inflow side of the slit is inclined forward in the rotation direction of the plurality of blades characterized in that an angle of at least the area of the front-side end surface of the inflow side of the slit to a radius passing through a center of the outflow opening in the circumferential direction is in a range of 1 to 45 degrees. the screen comprises a plurality of slits in a circumferential direction thereof and a screen member located between adjacent slits; the rotor and the screen are configured such that, by rotating at least the rotor, a fluid to be processed is discharged as an intermittent jet flow from inside to outside the screen through the plurality of slits; the screen forms a shape having a circular cross-section; an opening of the plurality of slits provided on an inner wall surface of the screen is made to serve as an inflow opening, and an opening of the plurality of slits provided on an outer wall surface of the screen is made to serve as an outflow opening; and a width (So) of the outflow opening in a circumferential direction is set to be narrower than a width (Si) of the inflow opening in a circumferential direction; the plurality of slits of the screen are defined by a front-side end surface and a back-side end surface arranged with a distance therebetween in the rotation direction of the plurality of blades, and at least an area of the front-side end surface of an inflow side of the slit is inclined forward in the rotation direction of the plurality of blades characterized in that an angle of at least the area of the front-side end surface of the inflow side of the slit to a radius passing through a center of the outflow opening in the circumferential direction is in a range of 1 to 45 degrees.