A planar-type optical isolator includes a substrate, a first mode splitter, a second mode splitter and a phase shift region formed on the substrate between the first mode splitter and the second mode splitter. The first mode splitter is formed on the substrate and receives an incident optical signal through an input port and splits the incident optical signal into a first incident mode and a second incident mode. The second optical splitter is formed on the substrate and combines a first rotated incident mode and a second rotated incident mode to reform the incident optical signal at an output port. The second mode splitter receives a reflected optical signal on the output port and splits the reflected optical signal into a first reflected mode and a second reflected mode. The phase shift region is formed on the substrate between the first mode splitter and the second mode splitter and includes a nonreciprocal phase shift section and reciprocal phase shift section.