In this study, the thermal environmental factors in a layer f(arm such as dry bulb temperature, relative humidity, black globe temperature and illumination intensity were measured and analyzed to serve as basis for effective design and plan of poultry houses. The correlation analysis between the different factors was also done. Heat Index as measure of the thermal stress was also calculated and analyzed. A $1,000m^2$ laying house, 4 meters high with 52,000 layers in six-stage type cages was used in the measurement of the different environmental parameters. The results were as follows; 1. The temperature of the inside air and materials was directly related to the increase in aerial temperature based on the dry-bulb, black globe temperature reading. The correlation factor of the outside to inside air based on dry bulb setting was very significant at 0.927 The dry bulb temperature for inside temperature ranged from $19.9~28.8^{circ}C;with;SD+2.2^{circ}C$ while that of the outside air was $16.2~33.1^{circ}C,;SD+3.5^{circ}C$. In addition, the temperature of the inside air was very stable. 2. The black globe temperature of the inside air ranged from $20.1~28.8^{circ}C,;SD+2.3^{circ}C$ while that of the outside air was $16.2~47.5^{circ}C,;SD+6.0^{circ}C$. 3. The relative humidity of the outside and inside air was $72.4~100;and;50.2~85.6\%$ with an average of $89.2;and;71.7\%$, respectively. 4. The illumination intensity in the laying house was less than 7 lux, with an average of $1.2~2.5lux$ relative to height indicating that the laying house was well isolated from outside radiation. 5. The heat index of the inside air of the laying house had a high variation from $20.5^{circ}C,;SD+2.5^{circ}C$ while that of the outside air was $13.1~45.5^{circ}C$, with an average of $21.6^{circ}C,;SD+6.3^{circ}C$