We investigate the quantum tunnel effect by nearest-neighbor double potential barriers. An explicit expression of the transmit ratio is obtained by a theoretical analysis. We show that the rate is invariant under space reflection. This result proposes a principal problem what is a "quantum" meaning of acceleration. The transmit ration is extremely complicate so that we use also numerical analyses to understand typical aspects of the tunnel effect. We discover that there appear new peaks in an energy region where incident particles cannot pass through the barriers classically. These novel aspects give us new insights in investigating electron conduction and also a technology of preventing radioactive rays.