Fluid mixer and apparatus using fluid mixer

A fluid mixer of the present invention has an element (1) and a chassis (2) that accommodates the element therein and that is engaged with at least both ends of the element, the element having: a first-flow-path forming section (13) at an end of which a fluid inlet (3) is formed and in which a first flow path (4) is formed; and a body section (12) at an end of which a fluid outlet (8) is formed, in which a second flow path (5) is formed, and on an outer circumferential surface of which a plurality of communicating holes (11) are formed so as to allow the second flow path to communicate with the outside. A plurality of delay members (9) are discontinuously formed in a flow-path axial direction on at least one of an inner circumferential surface of the chassis and the outer circumferential surface of the body section, a single continuous space is formed between the inner circumferential surface of the chassis and the outer circumferential surface of the body section, the space serves as a third flow path (6), and the communicating holes serve as branch flow paths (7).