A holder is provided for holding sockets. The holder includes a body, a lateral cover and a locking device. The body includes a lateral plate and a plurality of inserts extended from the lateral plate. The lateral cover is pivotally connected to the body and formed with a plurality of bosses. Each insert is adapted to be inserted into a first recess defined in one end of a corresponding socket and a corresponding boss is adapted to be inserted into a second recess defined in another end of the same socket. The locking device is used to lock the lateral cover to the body, thus locking the sockets in the holder.