Provided is a novel boron-containing compound. A compound represented by formula below is prepared and used. A black circle represents a B atom, and a white circle represents B-H； -R1 represents a group having 3-10 repeating sequences of -(CH2)n-X1-R3 (n represents an integer of 0-6； X1 represents O, S, NH, S-S, O-CO, NHCO, or SCO, or is absent； and R3 represents C6-C20 alkyl, hydroxy C6-C20 alkyl, amino C6-C20 alkyl, azido C6-C20 alkyl, hydroxycarbonyl C6-C20 alkyl, or the like) or -(CH2)2-O-, and having a methyl group or an ethyl group at the end of the oxygen atom side； and -R2 represents -(CH2)m-X2-R4 (m represents an integer of 0-8； X2 represents O, S, NH, S-S, O-CO, NHCO, or SCO, or is absent； and R4 represents a tumor recognition site) or is absent.本發明提供一種新穎之含硼化合物。本發明係製備下述式(I)所表示之化合物並加以使用。此處，黑點表示B原子，白點表示B-H；-R1表示於具有3次以上10次以下之-(CH2)n-X1-R3(n表示0至6之整數；X1表示O、S、NH、S-S、O-CO、NHCO或SCO，或者不存在；R3表示C6至C20烷基、羥基C6至C20烷基、胺基C6至C20烷基、疊氮C6至C20烷基、羥基羰基C6至C20烷基等)或者-(CH2)2-O-之重複排列且於氧原子側之末端具有甲基或乙基的基；以及-R2為-(CH2)m-X2-R4(m表示0至8之整數；X2表示O、S、NH、S-S、O-CO、NHCO或SCO，或者不存在；R4表示腫瘤識別部位)，或者不存在。
