A latch mechanism for locking a cover unit to a base unit which comprises a bottom panel and a cover panel defining a through hole therein, includes a latch member slidably installed to the bottom panel, a supporting member fixed to the bottom panel and defining a hole therein, a plug received in the hole of the supporting member, a resilient member placed between the supporting member and the bottom panel configured for resiliently driving the plug to move to make a top of the plug extend through the hole of the supporting member to engage in the through hole of the cover panel, and a hook protruding from the cover unit for extending through the through hole of the cover panel to drive the plug to move to engage with the latch member when covering the cover unit to the base unit.