The in situ detection method of dissolved molybdenum ions has been established by a channel flow double electrode. Mo(V)(sol) and Mo(VI)(sol) were detected on the collecting electrode, which was located at the downstream of the Mo working electrode, at 1.0 V and -0.4 V, respectively. Anodic dissolution of Mo in sulfuric acid solution was investigated by using the developed analytical method. Dissolved Mo(V)(sol) was detected in the passive region. In the transpassive region, both Mo(V)(sol) and Mo(VI)(sol) were detected, and these dissolutions were explained by chemical dissolutions from complicated oxides. The above-mentioned results were compared with the experimental results obtained by spectrophotometric determination.