Provided are an agitator and an agitating hook provided therein. The agitator includes a rotary shaft rotatably installed in a reactor, rotor blades installed at an outer circumference of the rotary shaft and rotated with the rotary shaft to agitate a material therein, and an agitating hook constituted by a pair of members spaced apart from each other at an inner wall of the reactor and through which the rotor blades pass. Here, a gap between the agitating hook is larger at an outlet port through which the rotor blade leaves than at an inlet port through which the rotor blade enters. Since a pressure is uniformly applied from the inlet port through which the rotor blade enters to the outlet port through which the rotor blade leaves, a torsional moment applied to the agitating hook is minimized. Therefore, it is possible to improve durability of the agitating hook and increase reliability of products.