This study focused on Japanese moral education for students in the teaching profession and empirically examined the educational effect of using online moral dilemma discussion (OMDD). As a pre-test, the participants filled up a questionnaire survey comprising the standard for public space (SPS) scales and communication skills (CS) by way of Microsoft Forms. Participants were then assigned to one of the following categories: paired OMDD, OMDD with five participants, and OMDD with five participants and a facilitator. Two Heinz dilemmas were used in OMDD as a topic of discussion. After the completion of OMDD, the post-test was carried out in the same way as the pre-test was. Accordingly, in the post-test for SPS, the score for "care for others" was significantly high, and the score for "egocentric" was significantly low. Regarding the result of multiple comparisons using the Bonferroni method, the OMDD score with five participants was determined to be higher than that of OMDD with five participants and a facilitator. Regarding CS, nonverbal, assertion, and discussion were significantly higher in the post-test. These results were discussed.