A heat dissipation device adapted for dissipating heat from a heat-generating electronic element, includes a plurality of fins assembled together. Each of the fins has a rectangular body and four arch-shaped flanges extending from edges of the body to form four round corners in four corners of the body. Each main body of the fins defines a plurality of locking members thereon to engage with corresponding locking members of a corresponding front fin. The arch-shaped flanges in four respective corners of the fins cooperate with each other to form four arced faces in four corners of the assembled fins along an entire length of the assembled fins.