A server and a signal analyzing device thereof are disclosed. The server includes a plurality of hard disk drive (HDDs), a plurality of indicators, at least a jumper, and a logic array. The logic array is coupled to the at least one jumper and includes a plurality of analyzing modules. The logic array selects one of the analyzing modules in response to the at least one jumper. The selected analyzing module analyzes an input signal and outputs a decoded signal. The indicators show the states of the HDDs according to the decoded signal.