Sound source localization is the method using the measurements of the acoustic signals from microphone arrays in acoustical engineering. This technique has been used broadly in 3-D sound technology, humanoid robot and teleconferencing and so on. For robot industry, their ultimate purpose is to be with human being. This is why the industry is demanding applicable robot's auditory system in the form of artificial ears like human's external ear such as ear pinna. It has more benefits to make use of auditory system with ear pinna to humanoid robots for HRI. In this paper, we propose a specific sound source localization method using a pair of artificial ears, each of which consisting of a single ear pinna and two microphones. The feasibility and localization performance of proposed method for speech signal in median plane is shown. Through the experiment in office environment, we confirm that robots with artificial ears can estimate the elevation angle of speech signal just using two microphone output signals.