A data management system comprising a plurality of nodes to be connected to and disconnected from a network, all of the plurality of nodes using the same type of data structure, wherein at least one of the plurality of nodes includes: a communicator that performs a communication via the network by using data having the data structure including a key; a database that accumulates the data; and a data analyzer that, when the node is newly connected to the network, provides another node already connected to the network with node information, the node information being used for enabling the node to serve as node for accumulating the data, wherein the node information of the plurality of nodes participating in the data management system is described in participation node information, the participation node information including for each node a node identification for identifying the node, processing capability of the node, and an operation rate of the node, when a second node (A-3) is newly connected to the network, the data analyzer of a first node (A-2) participating in the data management system is configured to read the participation node information and the key stored in the database of the first node (A-2) and output the read node information and the key to the second node (A-3), the data analyzer of the second node (A-3) is configured to acquire the node information and the key provided from the first node (A-2) and add its own node information to the acquired participation node information to be stored in the database of the second node (A-3), the data analyzer of the second node (A-3) is configured to output the participation node information to which its own node information is added to the first node (A-2) via the communicator, the data analyzer of the first node (A-2) is configured to write the participation node information to which the node information of the second node (A-3) is newly added to the database of the first node (A-2), the key includes a time at which the accumulated data was measured, the data analyzer selects the node of the operation rate greater than or equal to a predetermined threshold value as a node for saving the accumulated data, the data analyzer sets an allocation time range for allocating the accumulated data according to a measured time for each selected node by dividing a time range indicating a range of a time at which the accumulated data is measured in correspondence with the processing capability, and the data analyzer sets the allocation time range of a node having high processing capability to be longer than the allocation time range of a node having low processing capability. a communicator that performs a communication via the network by using data having the data structure including a key; a database that accumulates the data; and a data analyzer that, when the node is newly connected to the network, provides another node already connected to the network with node information, the node information being used for enabling the node to serve as node for accumulating the data, wherein the node information of the plurality of nodes participating in the data management system is described in participation node information, the participation node information including for each node a node identification for identifying the node, processing capability of the node, and an operation rate of the node, when a second node (A-3) is newly connected to the network, the data analyzer of a first node (A-2) participating in the data management system is configured to read the participation node information and the key stored in the database of the first node (A-2) and output the read node information and the key to the second node (A-3), the data analyzer of the second node (A-3) is configured to acquire the node information and the key provided from the first node (A-2) and add its own node information to the acquired participation node information to be stored in the database of the second node (A-3), the data analyzer of the second node (A-3) is configured to output the participation node information to which its own node information is added to the first node (A-2) via the communicator, the data analyzer of the first node (A-2) is configured to write the participation node information to which the node information of the second node (A-3) is newly added to the database of the first node (A-2), the key includes a time at which the accumulated data was measured, the data analyzer selects the node of the operation rate greater than or equal to a predetermined threshold value as a node for saving the accumulated data, the data analyzer sets an allocation time range for allocating the accumulated data according to a measured time for each selected node by dividing a time range indicating a range of a time at which the accumulated data is measured in correspondence with the processing capability, and the data analyzer sets the allocation time range of a node having high processing capability to be longer than the allocation time range of a node having low processing capability.