For the purpose of realizing high performance, high reliability, and more crew saving of merchant ships, the electronics and electronic techniques have been introduced and applied to marine systems. But, nowadays it seems very difficult to say that such new electronic technologies have been available enough to achieve our objectives, mainly because it is not easy to adapt system design, construction and operation from the viewpoint of the electronics. In particular, some of the difficulties are heavily due to the characteristics of the electronic devices, that is, they are very sensitive to electromagnetic noises with very small power. But, in spite of such situations, there have been not so many materials on how to suppress the noises induced in the electronic systems. Therefore, this report mainly summarizes how to enhance noise immunity and gives very effective and practical techniques for the marine electronic systems.