This research aims at (1) finding out and describing the implementation of lecturing method in the Islamic development of the prisoners in class II B Prison of Sleman Yogyakarta, (2) finding out and analyzing the result of Islamic development achievement, (3) finding out and explaining the supporting and inhibiting factors in fostering the Islamic development of the prisoners in Class II B Prison of Sleman Yogyakarta. This research used qualitative approach with qualitative descriptive type of research. The subjects were the Head of the Prison, counselors from the Ministry of Religion, and the prisoners. The data collection method was through: (1) interview, (2) observation and (3) documentation. The result shows that (1) the implementation of lecturing method in the Islamic development of the prisoners in Class II B Prison of Sleman Yogyakarta is through religious lecturing, short religious lecturing, Al-Qur‟an and Iqro recitation, and lecturing during the commemoration of Islamic holidays. (2) The result of the lecturing as the Islamic development has been quite effective and useful for the prisoners. For instances, they have achieved better moral improvement, better Islamic values understanding, better obedience in doing 5- time prayer, better social relationship with other prisoners (less quarrels between one and another), and better sense of regret for committing crimes. (3) The supporting factor in fostering the Islamic Development is that the Head of the Prison Class II B has been fully supporting the lecturing method itself. Another factor is the support from the counselors of the Ministry of Religion, in which they have contributed to the success of the Islamic development. Without the presence of the counselors, the Prison staff would find it difficult in providing a lecturing method as the Islamic development. The other factor is Islamic education books. The inhibiting factors are the limited number of counselors, inadequate facilities and infrastructures, convicts‟ hindering cases, and limited fund.