The present invention provides a method for producing a sealed .sup.210Pb--.sup.210Po .alpha. source (.alpha. particle emitter) and an apparatus thereof, which can be used as an .alpha. particle source for a random pulse generator. The method for producing a sealed .sup.210Pb--.sup.210Po .alpha. source (.alpha. particle emitter) includes the steps of: collecting .sup.210Pb--.sup.210Po with a .sup.210Pb collector using radon collection; precipitating the hydroxides of the collected .sup.210Pb--.sup.210Po and collecting the precipitates by a polycarbonate (PC) filter; dissolving the .sup.210Pb--.sup.210Po hydroxide precipitate to form a .sup.210Pb--.sup.210Po radioactive thin film; and sealing the .sup.210Pb--.sup.210Po radioactive thin film for protection.