An analytical device includes: a valve assembly that is connected to a plurality of gas supply conduits; and a gas supply chamber to which a plurality of gases are supplied through the valve assembly, wherein: the valve assembly includes a plurality of valves that regulate flow rates of the plurality of gases supplied to the gas supply chamber through the plurality of gas supply conduits, a fixing member that integrally fixes the plurality of valves, a plurality of first sealing members that seal the plurality of valves against the fixing member, and a retainer that is fastened to the fixing member to integrally press the first sealing member against the fixing member.