Silane coupling agent

Provided is a silane coupling agent which has a low viscosity and excellent coatability, and which has an excellent effect of improving the adhesion between an inorganic substance and an organic substance. The silane coupling agent of the present invention contains the following silicon compound and water, wherein the concentration of the silicon compound is 0.01-10 wt%. A silicon compound comprising a compound (I) represented by formula (1) and a polycondensate thereof, wherein the ratio of the content of the compound (I) to the content of a compound (II) having a weight-average molecular weight of 200-10000 in terms of standard polystyrene in the polycondensate of the compound (I) [compound (I)/compound (II); the weight ratio] is 1/99-95/5. 本发明提供低粘度且涂布性优异、提高无机物与有机物的粘接性的效果优异的硅烷偶联剂。本公开的硅烷偶联剂含有下述硅化合物和水，所述硅化合物浓度为0.01重量％～10重量％。硅化合物：包含下述式(1)所示的化合物(I)和其缩聚物，所述化合物(I)与化合物(I)的缩聚物中的基于标准聚苯乙烯换算的重均分子量为200～10000的化合物(II)的含量之比[化合物(I)/化合物(II)；重量比]为1/99～95/5。