A remote operation server having a function of mutual communication with a plurality of work machines and each of a plurality of remote operation devices for remotely operating one work machine to be remotely operated among the plurality of work machines, the remote operation server comprising: a state recognition element configured to recognize an index value indicating at least one of a level of a remote operation skill of an operator of each of the plurality of remote operation devices and a degree of difficulty of a work content through the one work machine; a communication resource allocation process element configured to perform a communication resource allocation process for allocating, to each of the plurality of remote operation devices, a communication resource for mutual communication with the one work machine, based on the index value recognized by the state recognition element; and an environment information control process element configured to perform an environment information control process for adjusting each of a plurality of environment information factors in different modes according to a difference in the communication resource allocated by the communication resource allocation process element so that a data amount of environment data is reduced, the environment information factor being output in an information output device mounted on each remote operation device and defining an information amount of environment information according to the environment data acquired by an environment recognition device included in the one work machine, the environment data indicating an environment of the one work machine, characterized in that the environment information control process element performs the environment information control process by classifying the plurality of environment information factors into a high environment information factor and a low environment information factor in different modes according to the difference in the operation state of the remote operation device or the motion state of the work machine that is recognized by the state recognition element, such that a reduction in an information amount of the environment information according to the low environment information factor is greater than a reduction in an information amount of the environment information according to the high environment information factor. a state recognition element configured to recognize an index value indicating at least one of a level of a remote operation skill of an operator of each of the plurality of remote operation devices and a degree of difficulty of a work content through the one work machine; a communication resource allocation process element configured to perform a communication resource allocation process for allocating, to each of the plurality of remote operation devices, a communication resource for mutual communication with the one work machine, based on the index value recognized by the state recognition element; and an environment information control process element configured to perform an environment information control process for adjusting each of a plurality of environment information factors in different modes according to a difference in the communication resource allocated by the communication resource allocation process element so that a data amount of environment data is reduced, the environment information factor being output in an information output device mounted on each remote operation device and defining an information amount of environment information according to the environment data acquired by an environment recognition device included in the one work machine, the environment data indicating an environment of the one work machine, characterized in that the environment information control process element performs the environment information control process by classifying the plurality of environment information factors into a high environment information factor and a low environment information factor in different modes according to the difference in the operation state of the remote operation device or the motion state of the work machine that is recognized by the state recognition element, such that a reduction in an information amount of the environment information according to the low environment information factor is greater than a reduction in an information amount of the environment information according to the high environment information factor.