PURPOSE: To realize a multi-beam radiation device and a multi-beam antenna having a feeder system in which a power supply of an amplifier is utilized with high efficiency by easily solving a problem of a power loss in the case of high power transmission and facilitating the setting of exciting distribution for a low side lobe.

CONSTITUTION: A cluster comprising plural antenna elements 1-22 is used for a primary radiator of a reflection mirror antenna sending/receiving a radio wave via a reflection mirror. Then amplifiers 211-232 are connected to each antenna element and a ratio of maximum output power of each amplifier is made coincident with a ratio of exciting power given to the antenna elements 1-22. Thus, fluctuation in the communication quantity between beams is solved flexibly and the power of the amplifiers 211-232 is effectively utilized and the antenna is effective to mobile communication or the like whose communication quantity fluctuates.