We often observe the reservoir heterogeneities on the pressure curve of the volcanic gas reservoir which brings some difficulty in analyzing by the conventional methods. As one of the analysis methods to resolve it, we assume that the heterogeneities are caused by the double porosity system, i.e. the fissure and matrix system. In that system, two parameters of ω: storatovity ratio, λ: interporosity flow coefficient control the pressure performance. This paper describes the analysis method of predicting these parameters by using the type curve matching, and as a result to apply this method to Minami-Nagaoka gas field, we obtained the conclusions as follows; 1. The idea of the double porosity system is applicable to Minami-Nagaoka gas field. 2. The well potential increases with ω. 3. No reduction of the recovery caused by the double porosity system can be estimated.