An obstacle monitoring system comprising: one or a plurality of construction machines; a server; and an information processing device, wherein the one or the plurality of construction machines, the server, and the information processing device being connected via a network, wherein each of the one or the plurality of construction machines includes: a machine main body (2, 3); a monitoring region setting unit which sets a monitoring region around the machine main body, the monitoring region being for monitoring entry of an obstacle; a plurality of obstacle sensing sensors (31L, 31R, 31B) arranged in the machine main body for sensing an obstacle entering the monitoring region from different directions; a storage unit; a storage processing unit which generates, when the obstacle has been sensed by at least one of the plurality of obstacle sensing sensors in a specific period, approach information indicating that the obstacle has been sensed to cause the storage unit to accumulatively store the approach information; and an output processing unit which outputs the approach information accumulatively stored in the storage unit in the specific period, wherein the server includes a log data storage unit which stores the approach information output from each of the one or the plurality of construction machines, and wherein the information processing device includes: a communication unit which obtains the approach information from the server; and a control unit which displays the obtained approach information on a display. one or a plurality of construction machines; a server; and an information processing device, wherein the one or the plurality of construction machines, the server, and the information processing device being connected via a network, wherein each of the one or the plurality of construction machines includes: a machine main body (2, 3); a monitoring region setting unit which sets a monitoring region around the machine main body, the monitoring region being for monitoring entry of an obstacle; a plurality of obstacle sensing sensors (31L, 31R, 31B) arranged in the machine main body for sensing an obstacle entering the monitoring region from different directions; a storage unit; a storage processing unit which generates, when the obstacle has been sensed by at least one of the plurality of obstacle sensing sensors in a specific period, approach information indicating that the obstacle has been sensed to cause the storage unit to accumulatively store the approach information; and an output processing unit which outputs the approach information accumulatively stored in the storage unit in the specific period, a machine main body (2, 3); a monitoring region setting unit which sets a monitoring region around the machine main body, the monitoring region being for monitoring entry of an obstacle; a plurality of obstacle sensing sensors (31L, 31R, 31B) arranged in the machine main body for sensing an obstacle entering the monitoring region from different directions; a storage unit; a storage processing unit which generates, when the obstacle has been sensed by at least one of the plurality of obstacle sensing sensors in a specific period, approach information indicating that the obstacle has been sensed to cause the storage unit to accumulatively store the approach information; and an output processing unit which outputs the approach information accumulatively stored in the storage unit in the specific period, wherein the server includes a log data storage unit which stores the approach information output from each of the one or the plurality of construction machines, and wherein the information processing device includes: a communication unit which obtains the approach information from the server; and a control unit which displays the obtained approach information on a display. a communication unit which obtains the approach information from the server; and a control unit which displays the obtained approach information on a display.