Abstract Numerical investigations of a differential equation describing a rf-biased Josephson junction, in which the interference term current is included, are carried out in some parameter region. The existanee of the intermittant transition to chaos is obtained and the critical exponent of the scaling law is determined in agreement with theoretical predictions. Furthermore, the Lyapunov exponent is calculated for several parameters, then the fractal dimension of strange attraetor dL is obtained, its dependence on the Lyapunov exponent is defined by Kaplan and Yorke. In addition, the Kolmogorov capacity of strange attractor dc is also calculated by box-counting algorithm. Such calculated values of dL and dc are close to each other as expected.