Experimental investigation on the characteristics of the air flow around a square prism located in a uniform flow with various angles of attack was carried out. Experimental results were obtained for the angle of attack from 0 .deg. to 45 .deg. and for Reynolds No. from $2.6{ imes}^4$to $12.8^4$. Seperation and reattachment was occurred on the forward face (face AB). Reattachment phenomenon was not developed in the range of attack angle lower 13 .deg. . But, for the range, 13 .deg. .approx. 35 .deg. , the reattachment developed and its position was moved forward the angle of attack increases. Pressure distributions on the reattachment face has a maxium at the reattachment point and a minimum at the separation point. Pressurea on two back faces are nearly symmetric in spite of the changes of the angle of attack and are influenced by the turbulence in rearward flow field.