PROBLEM TO BE SOLVED: To improve an acidic environment by culturing a bacterium belonging to the genus Acidocella, Acidiphilium, Acidobacterium or Thiobacillus in the presence of Al and removing Al from the acidic water environment or acidic soil. SOLUTION: One or more bacteria such a bacterium belonging to the genus Acidocella, Acidiphilium, Acidobacterium or Thiobacillus are cultured in the presence of 20-100mM of aluminum (Al) so that alumninum is removed from an acidic water environment or acidic soil and an acidic environment is simultaneously improved by alkalizing action by the presence of plural microorganisms.