A SIM card securing mechanism applied to a casing of a mobile phone is provided. The SIM card securing mechanism includes a SIM card holder used for carrying a SIM card, a restoring element, an elastic element, and a tenon structure. One end of the SIM card holder is connected to the casing, and the other end thereof has a first blocker. The SIM card holder may be rotated to be held in the casing or be exposed from a recess. One end of the elastic element is fixed on the casing. One end of the tenon structure is connected to the elastic element, and the other end thereof has a second blocker. The SIM card holder is rotated to allow the first blocker to be fastened with the second blocker via the resilience of the elastic element, and the SIM card holder may be held in the casing.