To prevent malfunctioning, accidental disability, stoppage, drop in accuracy and the like as caused by radio interference from a portable communication apparatus by a method wherein the intensity of an electric field from the portable communication apparatus is measured to be compared with a threshold of the intensity of the electric field causing a radio interference in an medical electric apparatus and a warning is given when any interference may be caused in the medical electric apparatus.

A radio wave 51 is received by an antenna 21 from a cellular phone 50 as portable communication apparatus to be amplified by a receiver circuit 32 of a control section 30 and an offsetting circuit 33 offsets a circuitry noise, an ambient noise or the like. A measuring circuit 34 offsets a signal from the receiver circuit 32 to measure the true intensity of an electric field from the portable communication apparatus and a specified value circuit 36 outputs a threshold for giving a warning. Moreover, a comparison judging circuit 37 compares a measured value from the measuring circuit 34 with a specified value to judge and outputs a warning when the measured value exceeds the threshold. A warning driving circuit 38 drives a warning means 40.