To provide a method for quickly producing a polycarboxylic acid metal complex useful as an adsorbent in high yield and productivity.

The metal complex is produced by reacting a polycarboxylic acid such as trans-1,4-cyclohexanedicarboxylic acid, terephthalic acid, trans, trans-4,4'-bicyclohexyldicarboxylic acid and nucleus-hydrogenated 2,6-naphthalenedicarboxylic acid with a salt of a metal such as copper, rhodium and nickel in the presence of a solvent while controlling the temperature in a relatively high temperature range of ≥120°C and ≤270°C. A carboxylic acid having high concentration can be used as the raw material and the method can be carried out especially without using an additive such as formic acid.