A method for manufacturing a stabilized metal nano particle solution is disclosed. This method manufactures a metal nano particle solution so as to make a metal substance such as silver, gold, copper, zinc or cobalt into ultra-capsular nano particles. That is to say, this new method is simple and suitable for mass production without requiring any separate reducer putting process at a room temperature while a transition metal nano particle solution is produced. In this method, an alcohol solution including a metal salt solution and a soluble polymer is mixed at a room temperature to make a nano metal particle solution with a particle size of 100 nm or less.