As a result of study of optimum conditions for the method of immobilizing a protein exhibiting an interaction with sugar chains on a substrate, it has been found that immobilization at an S/N ratio higher than in the prior art can be accomplished by applying a GTMS coat onto a surface of slide glass. Further, detection of any weak interaction between sugar chain and lectin with high sensitivity has been successfully accomplished by employing a substrate furnished with multiple reaction vessels lined with rubber having multiple holes and by carrying out lectin spotting and PBST washing. Moreover, through introduction of an evanescent excitation type scanner, it has become feasible to detect any interaction between lectin and sugar chain without the need to conduct washing removing operation for probe solution.