This invention provides an electrochemical analysis method for accurately detecting a harmful substance such as arsenic contained in a solution. In the electrochemical analysis method, a working electrode and a counter electrode are disposed in an object electrolytic solution. A negative potential is applied to the working electrode to electrodeposit the electrolyte onto the surface of the working electrode and thus to form an electrodeposit. Next, the potential of the working electrode is sweeped in a positive potential direction to allow the electrodeposit to elute into the solution and, at the same time, to detect a current change upon a potential change and thus to analyze an object substance dissolved as an electrolyte in the object electrolytic solution. A boron-doped electroconductive diamond electrode or an electrode with gold deposited on its surface is used as the working electrode.