Reading device and method for controlling reading device

A reading device connected to an external device, the reading device comprising:

• a transport section configured to transport a document;
• a reading section configured to read the document transported by the transport section;
• a data generation section configured to generate image data of the document read by the reading section;
• a transfer section configured to transfer the image data to the external device;
• a notification section configured to notify information to a user;
• and
• a control section, wherein
• the control section is configured to
• control a transport speed of the document by the transport section based on a transfer speed of the image data transferred by the transfer section and
• when the transfer speed is less than an improvement threshold value, cause the notification section to issue an improvement notification for prompting improvement of the transfer speed.