In this study, the direct contact melting of a porous material is investigated concerning the effects of the particle diameter, experimentally and analytically. The PCM is made of fine ice particles kept almost in a uniform diameter, which is changed as a parameter. The time dependency of the height of the PCM and the temperature of the heating surface are measured. In the analysis, two analytical models are proposed. One is calculated as the direct contact melting of the whole sample, and another is treated as the assembly of the direct contact melting of the individual particles. As the result, it was found that the amount of the melting increased with the increase in the particle diameter, due to the effects of the permeability in the case of small diameter. But, In the case of large diameter, amount of the melting decreased, as the particle diameter increased, because the direct contact melting occurred independently for the individual particles.