The different weather condition and the terrain of Ethiopia need a number of bridges to be constructed for every km length of the roads. Considering the nature of this need and construction of new roads, the Ethiopian government investing billions of birr for road sector development out of which more than 30% of the project cost is assigned to the construction of bridges. In spite of the large number of bridge construction in the country, the method of construction of cast in place concrete requires long time of construction and tremendous volume of false work. Furthermore, unexpected non-seasonal rainfall may occur at the upstream of bridge construction site and affect the constructed false work partially or damage it as a whole. Thus, this study has attempted to analyze, design and compare the cost of composite steel girder bridge and the reinforced concrete bridge which is designed by ERA manual. From the approximate structural analysis, design and cost comparison, the steel girder system offer a better economic alternative in view of overall cost of construction practiced in the country.