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Nitrous oxide (N2O) produced in shallow groundwater has two emission pathways to the atmosphere: dissolution in subsurface drainage and groundwater and later degassing from water surfaces open to the atmosphere, and upward gas diffusion. N2O undergoing upward diffusion through the soil surface cannot usually be distinguished from N2O produced in the topsoil. To evaluate the emission pathway and rate of groundwater-induced N2O, we conducted a one-year experiment using monolith lysimeters containing 1"m-long undisturbed Andosol. We measured emission of N2O via the soil surface and dissolved N2O emitted via subsurface drainage from the non-planted lysimeters under two conditions without fertilizer-nitrogen (N) addition: (1) with the groundwater table at 0.9 m depth (GW), and (2) without any groundwater table (nonGW). Total soil surface N2O emissions in the GW and nonGW treatments were 21.0±6.3 and 17.0±1.1"mg"N"m-2"yr-1, respectively (mean±standard error, n"="3), and the difference between the two treatments was not significant. Total dissolved N2O emissions via drainage in the GW and nonGW treatments were 11.40±5.68 and 0.42±0.03"mg"N"m-2"yr-1, respectively. The presence of groundwater significantly increased dissolved N2O emission under zero fertilizer-N addition. This is due to the one to three orders of magnitude higher concentration of dissolved N2O in the GW treatment. Our results indicate that the presence of groundwater increases total N2O emissions from an Andosol upland field via these two pathways.