A notification system including a plurality of notification devices each of which is a signal light and a management computer communicatively connected to the plurality of notification devices, wherein each notification device includes a notification portion including a display portion to variably display information by display color, an information accepting means to accept an information input from a control device controlling operation of a corresponding mechanical device, the information includes color information for specifying the display color to indicate a state of the corresponding mechanical device, a command receiving means to receive a command transmitted from the management computer, a notification control means to control the notification portion to make a notification according to the information which the information accepting means has accepted and to control the notification portion to make a notification according to the command which the command receiving means has received, and a transmitting means to transmit information corresponding to the information which the information accepting means has accepted to the management computer, and the management computer includes a receiving means to receive the information having been transmitted by the transmitting means of the plurality of notification devices, a storing means to store a rule for determining a priority of the plurality of notification devices, a determining means to apply the information which the receiving means has received to the rule and determine a priority of each of the plurality of notification devices and give a highest priority to a notification device of the plurality of notification devices, and a commanding means to transmit, to a notification device having been given the highest priority by the determining means, a highest priority notification command to order an execution of a highest priority notification indicating that the notification device is the highest priority notification device, wherein the rule is defined to rank the plurality of notification devices based on the information which the transmitting means of the notification devices transmit to the management computer. each notification device includes a notification portion including a display portion to variably display information by display color, an information accepting means to accept an information input from a control device controlling operation of a corresponding mechanical device, the information includes color information for specifying the display color to indicate a state of the corresponding mechanical device, a command receiving means to receive a command transmitted from the management computer, a notification control means to control the notification portion to make a notification according to the information which the information accepting means has accepted and to control the notification portion to make a notification according to the command which the command receiving means has received, and a transmitting means to transmit information corresponding to the information which the information accepting means has accepted to the management computer, and the management computer includes a receiving means to receive the information having been transmitted by the transmitting means of the plurality of notification devices, a storing means to store a rule for determining a priority of the plurality of notification devices, a determining means to apply the information which the receiving means has received to the rule and determine a priority of each of the plurality of notification devices and give a highest priority to a notification device of the plurality of notification devices, and a commanding means to transmit, to a notification device having been given the highest priority by the determining means, a highest priority notification command to order an execution of a highest priority notification indicating that the notification device is the highest priority notification device, wherein the rule is defined to rank the plurality of notification devices based on the information which the transmitting means of the notification devices transmit to the management computer.