The wettabilities of poly(caproamide)(PCA) and poly(ethylene terephthalat)(PET) were investigated in terms of the heat of wetting and the contact angle. In the range of temperatures between 20$^{circ}C$ and 70$^{circ}C$, the heat of wetting was measured using an adiabatic calorimeter, and the advancing contact angle was determined by means of a vertical plate method. The following results were obtained 1) For PET in water, both of the heat of wetting and the advancing contact angle slightly decreased with increase of temperature. The temperature coefficient of the contact angle was obtained to be about -0.13deg/$^{circ}C$. The two transition temperatures for PET were found at around 25$^{circ}C$ and 70$^{circ}C$, respectively. 2) The heat of wetting could be calculated from the temperature coeficient values of the contact angle. The calculated values at 20$^{circ}C$ were about 51 erg/$ extrm{cm}^2$ for PCA and about 13 erg/$ extrm{cm}^2$ for PET, respectively. 3) The heat of wetting of PCA in water-ethanol mixture was higher than that of PET. For PCA, the heat of wetting increased as the surface tension of liquid increased. On the other hand, for PET, the value slightly decreased to the minimum, and then gradually increased. 4) It was confirmed that the structural properties of fiber can be at least partially estimated by measuring the contact angle and the heat of wetting.