This study examined the relationships between the reasons for confessions and interviewing styles by administering a self-reported questionnaire to new male adult prison inmates across Japan. The three factors proposed by Gudjonsson and his colleagues (1991, 1992, 1994, 1999), namely, perception of proof, internal pressure, and external pressure, were investigated. When participants had decided to confess prior to interviews, they were more likely to confess due to perception of proof and internal pressure compared to their counterparts. Furthermore, participants who experienced a relationship-focused interviewing style, which stressed active listening and rapport-building while talking about the criminal incidents directly, were more likely to confess due to internal pressure and less likely to confess due to external pressure.