An electrochemical device includes an electrochemical cell, an oxidizer gas supply portion, and a first contaminant trap portion. The electrochemical cell includes an anode, a cathode, and a solid electrolyte layer provided between the fuel cell and the cathode. The oxidizer gas supply portion includes an oxidizer gas supply port for supplying oxidizer gas to the cathode. The first contaminant trap portion is provided between the cathode and the oxidizer gas supply port and configured to adsorb contaminants contained in the oxidizer gas. At least part of the first contaminant trap portion is disposed 20 mm or less from the oxidizer gas supply port in a gas supply direction in which the oxidizer gas is supplied from the oxidizer gas supply port.