In an agitation mixing apparatus 51 which includes: a casing 52 having a flow path 56 in which a fluid flows; an agitator 53 which is disposed inside the casing 52 and includes a shaft 57 and a vane 58 mounted around the shaft 57; and a drive source 59, connected to the shaft 57, for vibrating the agitator 53 in an axial direction, grooves 71 are provided on an inner wall surface of the casing 52 at predetermined intervals in the axial direction.