Mounting structure of a mounted component, light scanning device, and image forming apparatus

A mounting structure for a mounted component, the structure comprising:

• a holding member that holds a mounted component comprising a light source, the position of the holding member being adjusted within a plane that is substantially orthogonal to an optical axis of the light source;
• a shaft portion that projects from a side surface of a case body in which the light source is provided, in a direction along the optical axis of the light source;
• and
• a fixing member in which a contact portion that contacts the shaft portion is provided, wherein in a state in which the contact portion contacts the shaft portion, rotation of the fixing member around two axes that are substantially orthogonal to the optical axis is limited to an allowable range, and the fixing member is adhered, by a cured resin cured by a curing member, to a surface of the holding member facing toward the fixing member in the direction along the optical axis, and is fixed by the cured resin to the shaft portion.