In recent years, developments of high-speed network infrastructure have been progressed. However, demands for information retrieval through narrow band lines are still exist as getting safety information in an emergency and information for navigating vessels in the inland sea, since in such situations, improper conditions for networks including traffic congestions and/or physical troubles are likely to occur. The use of mobile agent is a method which enables to transmit data even in such improper conditions. Hence, focusing on the function to retransmit mobile agent, we conduct computer simulations with introducing the following two parameters of mobile agent in unstable communication environments; the number of migrations and the number of produced mobile agents traveling all servers. The simulations confirmed that the ability of mobile agent in collecting information can be enhanced by setting the retransmission period of a mobile agent to the average time for its migration between two servers.