A terminal crimping apparatus includes an anvil for supporting a metal terminal including a base plate portion for placing an electric wire thereon and a pair of crimping piece portions extending upwardly respectively from opposite side edges of the base plate portion and a crimper which includes a press-deforming portion having a generally arch-shape formed of two arc-shaped surfaces which are opposed to the anvil. The anvil and the crimper cooperate to press the crimping piece portions for crimping the crimping piece portions to the electric wire placed on the metal terminal. The shape of the crimper satisfies a formula, Index a=c·cos θ, where c represents a length of the arc-shaped surface of the crimper, and θ represents an angle formed by a tangential line to the arc-shaped surface at a central portion of the crimper and a vertical line.