A data collecting apparatus is used in a survey system in which research data such as television audience ratings and market research data is collected by a data collecting device provided in each of a plurality of panelists' homes, the collected research data is sent to a data center through telephone links, and, at the data center, the data is processed with the aid of a large scale computer to calculate desired research data. The data collecting apparatus includes a channel detector for detecting a television channel being viewed, a market research data entry device, a personal data entry device, and a data processing device for storing and processing the entered data. The detected channel data and the entered personal data are transferred to the data processing device via domestic power supply lines. The market research data is efficiently entered with the aid of a bar-code reader and a keyboard in a sequence-non-ordered manner. The personal data is entered with an entry device using infrared light. The personal data entry device may have picture-like illustration images of respective panelists so that they need not remember personal identification numbers.