This paper investigates a relationship between the intensity of EM radiation and that of EM information leakage on a cryptographic device. For this purpose, we first observe an EM-field map on a cryptographic device by an EM scanning system, and then perform simple electromagnetic analysis (SEMA) experiments at some distinct points on the device including over the module. The target device considered here is a Side-channel Attack Standard Evaluation Board (SASEBO) with an RSA hardware implemented in an FPGA. Through the experiment, we demonstrate which points are effective for EM information leakage. The result suggests that the position of greatest EM intensity is not always the most effective point in EM information leakage.