當然可以，像下面這個例子就在類外定義：#include "stdafx.h"#include <iostream>class Complex //複數類{public:double real;//實數double imag;//虛數Complex(double real=0,double imag=0){this->real=real;this->imag=imag;}};Complex operator+(Complex com1,Complex com2)//運算子過載函式{return Complex(com1.real+com2.real,com1.imag+com2.imag);}int main(){Complex com1(10,10),com2(20,20),sum;sum=com1+com2;//或sum=operator+(com1,com2)std::cout<<"sum的實數部分為"<<sum.real<<std::endl;std::cout<<"sum的虛數部分為"<<sum.imag<<"i"<<std::endl;return0;}