The particle dynamics in a gas-solid contactor with inclined baffle plates forming a zig zag path have been numerically simulated by a two-fluid model. In this contactor, solid particles slide down along the baffle plates and are fluidized at the openings between the wall and the edge of the baffle plates by the upflowing gas. Thus this structure is called a "moving-fluidized bed." In the present two-fluid model, both the gas and particles are considered to be in continuum and fully interpenetrating and their behavior are described in terms of four hydrodynamic equations; conservation equations of mass and momentum for the respective phases. The computer simulated porosity distributions in a tao dimensional moving-fluidized bed show that the gas bubbles appear in the fluidized bed region at the opening for the gas velocity exceeding a critical value. The average diameter of the bubbles and the distribution of the particle velocity along the baffle plate have been calculated. These results are in good agreement with the experimental results.