We have found phase separation in La0.45Sr0.55MnO3-δ (LSMO) by means of electron spin resonance, magneticforce microscopy (MFM) and magnetic measurements. Ferromagnetic and antiferromagnetic phases can coexist at lowtemperatures, and ferromagnetic and paramagnetic phases coexist when the temperature lies between the Neel andCurie temperatures. The size and shape of the ferromagnetic phases (the minority phases) was first observed directlyfrom MFM images. It is suggested that the phase separation in LSMO is not the charge segregation type, but anelectroneutral type due perhaps to the nonuniform distribution of oxygen vacancies.