An automatic injection device is provided herein comprising a container body having a distal end and a proximal end； a piston locked at said proximal end of said container body before medication injection； a spring configured to bias said piston distally； a releasable restraining means configured to releasably restrain said piston in a locked state against said biasing of said spring, wherein, upon release of said releasable restraining means, said piston moves under force of said spring toward said distal end of said container body； an activation means configured to release said releasable means； a needle cap placed at said distal end of said container body； and a needle placed at said distal end of said container body.
