The phase array composed form spiral microstrip radiators is considered. This array can be applied as radiation focusing spiraphase lens. The lack of traditional phase shifters ensures good cost, technological and constructive characteristics of spiraphase arrays in a microwave range. Antenna construction and mathematical model are considered. This device permits to realize a focusing of antenna feed field by a microstrip antenna array. The microstrip element shape is arbitrary. The mathematical model is obtained by integral equation method. Microstrip spiral radiators current distribution and input impedance are investigated. The numerical results can be used to develop antennas with optimum parameters.