PROBLEM TO BE SOLVED: To provide a critical call system capable of having an appropriate person come.SOLUTION: A biological information monitor 100 is provided with a support request button 125. When the support request button 125 is operated, the biological information monitor 100 performs multicast transmission to other biological information monitors. Thereby, a critical call system that can have an appropriate person come to give support quickly can be achieved without troubling a support request side under a tense situation.