Skybox Studio that can stabilize (level the horizon) of your 360 video. Here is a tutorial and demo by CreatorUp.
360 videos need a level horizon for viewer comfort. There are a few possibilities for stabilizing a moving 360 camera. One is to use a stabilized gimbal such as the Guru 360. Another approach is to use software. One such software is Skybox Studio, a plugin for Adobe After Effects or Premiere Pro.
Here is CreatorUp's tutorial for stabilizing your video with Skybox Studio:
Here is the official page for Skybox Studio.