A quantum dot coupled to two electrodes with spin-dependent splitting of chemical potentials (spin bias) is proposed as a detector of an individual electron spin. Spin polarized transport properties through the quantum dot have been investigated theoretically by means of the nonequilibrium Green's function formalism. We found that the direction of current flow is dependent on the electronic spin state in quantum dot. Measuring the direction of the current flow through the devices, we can determine the direction of the electronic spin state in quantum dot. This proposed detector provides a practical and all electrical approach to detect the electronic spin state in quantum dot structure.