根据欧盟法律：
If you are an EU national , you do not need to show your national ID card or passport when you are travelling from one border-free Schengen EU country to another.

Even if you don’t need a passport for border checks within the Schengen area , it is still always highly recommended to take a passport or ID card with you, so you can prove your identity if needed (if stopped by police, boarding a plane, etc.). Schengen EU countries have the possibility of adopting national rules obliging you to hold or carry papers and documents when you are present on their territory.

Driving licences, post, bank or tax cards are not accepted as valid travel documents or proof of identity.

相关翻译：

如果您是欧盟公民（持有欧盟护照），从一个无国界申根欧盟国家到另一个无国界申根欧盟国家旅行时，无需出示您的国家身份证或护照。

即使您在申根地区不需要护照进行边境检查，仍然强烈建议您随身携带护照或身份证，以便在需要时证明您的身份（如果被警察拦下、登机等）。申根欧盟国家有可能采用国家规定，要求您在其领土上持有或携带文件和文件。

驾驶执照、邮政、银行或税务卡不被视为有效的旅行证件或身份证明。