A method for producing an objective substance, the method comprising: producing the objective substance by using a microorganism having an ability to produce the objective substance, wherein the microorganism has a feature selected from the group consisting of: (A-i) the microorganism has been modified so that the activity of AICAR formyltransferase and/or IMP cyclohydrolase is reduced as compared with a non-modified strain by means of attenuating the expression of a gene encoding AICAR formyltransferase and/or IMP cyclohydrolase and/or by means of disrupting a gene encoding AICAR formyltransferase and/or IMP cyclohydrolase, (A-ii) the microorganism has been modified so that a gene encoding AICAR formyltransferase and/or IMP cyclohydrolase has a mutation that improves the ability of the microorganism to produce the objective substance, and (A-iii) combinations thereof; wherein the objective substance is selected from the group consisting of: metabolites selected from the group consisting of vanillin, vanillic acid, melatonin, ergothioneine, mugineic acid, ferulic acid, spermidine, spermine, guaiacol, 4-vinylguaiacol, 4-ethylguaiacol, creatine, and combinations thereof; L-methionine; and combinations thereof. producing the objective substance by using a microorganism having an ability to produce the objective substance, wherein the microorganism has a feature selected from the group consisting of: (A-i) the microorganism has been modified so that the activity of AICAR formyltransferase and/or IMP cyclohydrolase is reduced as compared with a non-modified strain by means of attenuating the expression of a gene encoding AICAR formyltransferase and/or IMP cyclohydrolase and/or by means of disrupting a gene encoding AICAR formyltransferase and/or IMP cyclohydrolase, (A-ii) the microorganism has been modified so that a gene encoding AICAR formyltransferase and/or IMP cyclohydrolase has a mutation that improves the ability of the microorganism to produce the objective substance, and (A-iii) combinations thereof; (A-i) the microorganism has been modified so that the activity of AICAR formyltransferase and/or IMP cyclohydrolase is reduced as compared with a non-modified strain by means of attenuating the expression of a gene encoding AICAR formyltransferase and/or IMP cyclohydrolase and/or by means of disrupting a gene encoding AICAR formyltransferase and/or IMP cyclohydrolase, (A-ii) the microorganism has been modified so that a gene encoding AICAR formyltransferase and/or IMP cyclohydrolase has a mutation that improves the ability of the microorganism to produce the objective substance, and (A-iii) combinations thereof; wherein the objective substance is selected from the group consisting of: metabolites selected from the group consisting of vanillin, vanillic acid, melatonin, ergothioneine, mugineic acid, ferulic acid, spermidine, spermine, guaiacol, 4-vinylguaiacol, 4-ethylguaiacol, creatine, and combinations thereof; L-methionine; and combinations thereof. metabolites selected from the group consisting of vanillin, vanillic acid, melatonin, ergothioneine, mugineic acid, ferulic acid, spermidine, spermine, guaiacol, 4-vinylguaiacol, 4-ethylguaiacol, creatine, and combinations thereof; L-methionine; and combinations thereof.