We have mechanically fabricated Ni and Pd nanoconstrictions and investigated their conductance characteristics in solution under electrochemical potential control. When the electrochemical potential of the Ni and Pd nanoconstrictions was kept at the hydrogen evolution potential, clear features appeared at 1−1.5 G₀ (G₀ = 2e²/h) and at 1 G₀ in the conductance histogram of Ni and Pd, respectively. Based on the experimental results previously obtained in ultra high vacuum at ultra low temperature and theoretical calculation, the peaks observed in the present system (1−1.5 G₀ for Ni, 1 G₀ for Pd) were assigned to the mono atomic contact. While the fabrication of mono atomic contacts of Ni and Pd is difficult at room temperature, the mono atomic contacts could be stabilized in solution by hydrogen adsorption. The stability of the Pd atomic contact was qualitatively analyzed using conductance traces. The atomic contact could be stretched 0.4 nm in length just before breaking, suggesting the formation of the Pd wire.