The present invention relates to a biodegradable polymer microsphere-containing sustained-release injection containing escitalopram as an active ingredient, and to a method for manufacturing the same. In the case of escitalopram microspheres, there is a problem of low encapsulation rate, fracture due to weak strength, and initial over-release due to the phase separation of the liquid drug and the polymer inside the microspheres. In order to solve the problem, it is possible to maximize the encapsulation amount and the encapsulation efficiency of the escitalopram adding a hydrophobic solidifying agent to uniformize the non-uniform phase, to overcome the cracking of the microspheres at high loading conditions, and to properly control the initial release and release delay of the microspheres.