Visualization of sound information has many interests for understanding sound fields. Especially, sound source localization using a microphone array is helpful for sound source separations, acoustical design, abnormality detection, etc. However, three-dimensional (3D) sound source localization result is difficult to present intuitively on ordinary displays. On the other hand, in recent years, mixed reality (MR) technology has rapidly developed and attracts many attentions. MR devices install many sensors, displays, and ICT technologies, which realize interaction between real environment and virtual spaces. In this paper, we propose an MR display system for 3D sound source localization results, which are obtained from a microphone array data. MR technology enables presentation of 3D sound source localization results which is difficult for ordinary displays. In addition, the user can observe both 3D sound source localization results and the environment simultaneously.