To provide a bonding structure in which bonding strength is improved when a low viscosity bonding agent such as an instant glue is used for bonding, a bonding agent is easily flowed into bonded surfaces, a working property is efficient, and the bonding agent is not risen on a surrounding portion.

In the bonding structure bonding a first member and a second member, the low viscosity bonding agent is flowed into a bonded surfaces, in a state in which at least a part of a designated surface of the first and second members is kept in contact with each other as respective bonded surfaces. At least a groove extending to an outer periphery of the bonded surface is formed on at least one side of the bonded surfaces of the first and second members.