A blocking mechanism includes a chassis, a blocking member, and a resilient member. The chassis is configured to secure a circuit board, the chassis comprising a locking structure. The blocking member is configured to abut the circuit board, for preventing the circuit board from sliding towards the blocking member. The blocking member includes a positioning structure slidably engaged with the locking structure. The resilient member is secured to the blocking member and engaged with the locking structure for preventing the blocking member from sliding relative to the locking structure. The resilient member is resiliently deformable. When the resilient member is disengaged from the locking structure, the blocking member is slidable relative to the chassis to disengage the locking structure from the positioning structure.