A rectangular probe of a probe card device includes a metallic pin and a metallic reinforcing body. The metallic pin includes a middle segment, a first connecting segment and a second connecting segment respectively extending from two opposite ends of the middle segment, a first contacting segment extending from the first connecting segment in a direction away from the middle segment, and a second contacting segment extending from the second connecting segment in a direction away from the middle segment. The metallic reinforcing body is integrally formed on the middle segment. The Young's modulus of the metallic reinforcing body is larger than that of the metallic pin. The electric conductivity of the metallic pin is larger than that of the metallic reinforcing body. An outside diameter jointly formed by the metallic reinforcing body and the middle segment is larger than an outside diameter of the second connecting segment.