The disclosure provides a server including casing, detecting device and cover plate. The casing includes bottom plate, first side plate and second side plate. The first side plate or the second side plate includes an engaging slot. The engaging slot includes fixing part and releasing part that are connected to each other. The edge of first side plate includes hole. The detecting device include switch and controller. The cover plate includes cover portion, first side wall, second side wall, engaging component and protrusion. The cover plate includes fixed position and removable position. When cover plate is located in fixed position, engaging component is located in fixing part, such that cover plate is fixed on casing and protrusion penetrates through hole to push switch. When cover plate is located in removable position, engaging component is located in releasing part, and protrusion is moved away from switch.