We have carried out soft x-ray photoemission experiments on itinerant ferromagnet Sr1-x(La0.5K0.5)xRuO3 to investigate how the electronic state varies with doping concentration. The Ru 4d-derived coherent part of the valence spectra develops significantly with increasing x for x≤0.3, which can be explained by the suppression of the ferromagnetic exchange splitting. With further increasing x, this development is overwhelmed by the spectral weight transfer from the coherent to the incoherent parts due to the electron correlation. The enhancement of the electron correlation effect with doping is also confirmed by the Ru 3d core-level spectra as the suppression of the well-screened peak. In contrast to the remarkable variation of the Ru 4d spectral intensity as a function of x, the valence spectra hardly depend on temperature and do not show any noticeable change across the magnetic transition temperatures, indicating that the temperature dependence of the exchange splitting cannot be explained by a simple Stoner picture. We compare the present photoemission results with those for isostructural Sr1-xAxRuO3 (A=La and Ca) and discuss the origin of the difference in the magnetic property between these doped compounds.