Quantum interference properties of GaAs/AlGaAs symmetric double quantum wells were investigated in a magnetic field parallel to heterointerfaces at 1.9 K. For two types of samples used in our experiments, two GaAs quantum wells with the same width of 60 are separated by an AlGaAs barrier layer of 120 and 20 thick, respectively. The channels with the length of 2 μm are defined by alloyed ohmic contacts. The conductance oscillation as a function of the magnetic flux Φ(=B/s) was observed and oscillation period is approximately equal to h/e. The results are in agreement with the theoretical expectation of the Aharonov-Bohm effect. Conductance oscillations are apparent slightly in the samples with a thinner AlGaAs barrier.