Molecular dynamics simulation was carried out to estimate volume expansion coefficients and compressibility of solid and liquid silicon. The numerical simulation employed constant temperature and pressure algorithms based on Andersen's method. Stillinger-Weber potential was used as a model potential. Calculated result shows no anomaly of density in the melt near the melting point. Estimated thermal-expansion coefficients of the solid and the melt are 1.4x10^<-5>K^<-1> and 0.4x10^<-4> K^<-1>, respectively. Calculated compressibility of the solid and the melt is almost identical to experimental data.